2020-07-04 13:35:49 +00:00
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/* Initialize x86 cache info.
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2023-01-06 21:08:04 +00:00
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Copyright (C) 2020-2023 Free Software Foundation, Inc.
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2020-07-04 13:35:49 +00:00
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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static const struct intel_02_cache_info
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{
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unsigned char idx;
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unsigned char assoc;
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unsigned char linesize;
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unsigned char rel_name;
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unsigned int size;
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} intel_02_known [] =
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{
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#define M(sc) ((sc) - _SC_LEVEL1_ICACHE_SIZE)
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{ 0x06, 4, 32, M(_SC_LEVEL1_ICACHE_SIZE), 8192 },
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{ 0x08, 4, 32, M(_SC_LEVEL1_ICACHE_SIZE), 16384 },
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{ 0x09, 4, 32, M(_SC_LEVEL1_ICACHE_SIZE), 32768 },
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{ 0x0a, 2, 32, M(_SC_LEVEL1_DCACHE_SIZE), 8192 },
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{ 0x0c, 4, 32, M(_SC_LEVEL1_DCACHE_SIZE), 16384 },
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{ 0x0d, 4, 64, M(_SC_LEVEL1_DCACHE_SIZE), 16384 },
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{ 0x0e, 6, 64, M(_SC_LEVEL1_DCACHE_SIZE), 24576 },
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{ 0x21, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 262144 },
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{ 0x22, 4, 64, M(_SC_LEVEL3_CACHE_SIZE), 524288 },
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{ 0x23, 8, 64, M(_SC_LEVEL3_CACHE_SIZE), 1048576 },
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{ 0x25, 8, 64, M(_SC_LEVEL3_CACHE_SIZE), 2097152 },
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{ 0x29, 8, 64, M(_SC_LEVEL3_CACHE_SIZE), 4194304 },
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{ 0x2c, 8, 64, M(_SC_LEVEL1_DCACHE_SIZE), 32768 },
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{ 0x30, 8, 64, M(_SC_LEVEL1_ICACHE_SIZE), 32768 },
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{ 0x39, 4, 64, M(_SC_LEVEL2_CACHE_SIZE), 131072 },
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{ 0x3a, 6, 64, M(_SC_LEVEL2_CACHE_SIZE), 196608 },
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{ 0x3b, 2, 64, M(_SC_LEVEL2_CACHE_SIZE), 131072 },
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{ 0x3c, 4, 64, M(_SC_LEVEL2_CACHE_SIZE), 262144 },
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{ 0x3d, 6, 64, M(_SC_LEVEL2_CACHE_SIZE), 393216 },
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{ 0x3e, 4, 64, M(_SC_LEVEL2_CACHE_SIZE), 524288 },
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{ 0x3f, 2, 64, M(_SC_LEVEL2_CACHE_SIZE), 262144 },
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{ 0x41, 4, 32, M(_SC_LEVEL2_CACHE_SIZE), 131072 },
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{ 0x42, 4, 32, M(_SC_LEVEL2_CACHE_SIZE), 262144 },
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{ 0x43, 4, 32, M(_SC_LEVEL2_CACHE_SIZE), 524288 },
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{ 0x44, 4, 32, M(_SC_LEVEL2_CACHE_SIZE), 1048576 },
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{ 0x45, 4, 32, M(_SC_LEVEL2_CACHE_SIZE), 2097152 },
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{ 0x46, 4, 64, M(_SC_LEVEL3_CACHE_SIZE), 4194304 },
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{ 0x47, 8, 64, M(_SC_LEVEL3_CACHE_SIZE), 8388608 },
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{ 0x48, 12, 64, M(_SC_LEVEL2_CACHE_SIZE), 3145728 },
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{ 0x49, 16, 64, M(_SC_LEVEL2_CACHE_SIZE), 4194304 },
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{ 0x4a, 12, 64, M(_SC_LEVEL3_CACHE_SIZE), 6291456 },
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{ 0x4b, 16, 64, M(_SC_LEVEL3_CACHE_SIZE), 8388608 },
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{ 0x4c, 12, 64, M(_SC_LEVEL3_CACHE_SIZE), 12582912 },
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{ 0x4d, 16, 64, M(_SC_LEVEL3_CACHE_SIZE), 16777216 },
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{ 0x4e, 24, 64, M(_SC_LEVEL2_CACHE_SIZE), 6291456 },
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{ 0x60, 8, 64, M(_SC_LEVEL1_DCACHE_SIZE), 16384 },
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{ 0x66, 4, 64, M(_SC_LEVEL1_DCACHE_SIZE), 8192 },
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{ 0x67, 4, 64, M(_SC_LEVEL1_DCACHE_SIZE), 16384 },
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{ 0x68, 4, 64, M(_SC_LEVEL1_DCACHE_SIZE), 32768 },
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{ 0x78, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 1048576 },
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{ 0x79, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 131072 },
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{ 0x7a, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 262144 },
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{ 0x7b, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 524288 },
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{ 0x7c, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 1048576 },
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{ 0x7d, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 2097152 },
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{ 0x7f, 2, 64, M(_SC_LEVEL2_CACHE_SIZE), 524288 },
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{ 0x80, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 524288 },
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{ 0x82, 8, 32, M(_SC_LEVEL2_CACHE_SIZE), 262144 },
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{ 0x83, 8, 32, M(_SC_LEVEL2_CACHE_SIZE), 524288 },
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{ 0x84, 8, 32, M(_SC_LEVEL2_CACHE_SIZE), 1048576 },
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{ 0x85, 8, 32, M(_SC_LEVEL2_CACHE_SIZE), 2097152 },
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{ 0x86, 4, 64, M(_SC_LEVEL2_CACHE_SIZE), 524288 },
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{ 0x87, 8, 64, M(_SC_LEVEL2_CACHE_SIZE), 1048576 },
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{ 0xd0, 4, 64, M(_SC_LEVEL3_CACHE_SIZE), 524288 },
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{ 0xd1, 4, 64, M(_SC_LEVEL3_CACHE_SIZE), 1048576 },
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{ 0xd2, 4, 64, M(_SC_LEVEL3_CACHE_SIZE), 2097152 },
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{ 0xd6, 8, 64, M(_SC_LEVEL3_CACHE_SIZE), 1048576 },
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{ 0xd7, 8, 64, M(_SC_LEVEL3_CACHE_SIZE), 2097152 },
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{ 0xd8, 8, 64, M(_SC_LEVEL3_CACHE_SIZE), 4194304 },
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{ 0xdc, 12, 64, M(_SC_LEVEL3_CACHE_SIZE), 2097152 },
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{ 0xdd, 12, 64, M(_SC_LEVEL3_CACHE_SIZE), 4194304 },
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{ 0xde, 12, 64, M(_SC_LEVEL3_CACHE_SIZE), 8388608 },
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{ 0xe2, 16, 64, M(_SC_LEVEL3_CACHE_SIZE), 2097152 },
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{ 0xe3, 16, 64, M(_SC_LEVEL3_CACHE_SIZE), 4194304 },
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{ 0xe4, 16, 64, M(_SC_LEVEL3_CACHE_SIZE), 8388608 },
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{ 0xea, 24, 64, M(_SC_LEVEL3_CACHE_SIZE), 12582912 },
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{ 0xeb, 24, 64, M(_SC_LEVEL3_CACHE_SIZE), 18874368 },
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{ 0xec, 24, 64, M(_SC_LEVEL3_CACHE_SIZE), 25165824 },
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};
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#define nintel_02_known (sizeof (intel_02_known) / sizeof (intel_02_known [0]))
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static int
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intel_02_known_compare (const void *p1, const void *p2)
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{
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const struct intel_02_cache_info *i1;
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const struct intel_02_cache_info *i2;
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i1 = (const struct intel_02_cache_info *) p1;
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i2 = (const struct intel_02_cache_info *) p2;
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if (i1->idx == i2->idx)
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return 0;
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return i1->idx < i2->idx ? -1 : 1;
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}
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static long int
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__attribute__ ((noinline))
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intel_check_word (int name, unsigned int value, bool *has_level_2,
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bool *no_level_2_or_3,
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const struct cpu_features *cpu_features)
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{
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if ((value & 0x80000000) != 0)
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/* The register value is reserved. */
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return 0;
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/* Fold the name. The _SC_ constants are always in the order SIZE,
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ASSOC, LINESIZE. */
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int folded_rel_name = (M(name) / 3) * 3;
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while (value != 0)
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{
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unsigned int byte = value & 0xff;
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if (byte == 0x40)
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{
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*no_level_2_or_3 = true;
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if (folded_rel_name == M(_SC_LEVEL3_CACHE_SIZE))
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/* No need to look further. */
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break;
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}
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else if (byte == 0xff)
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{
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/* CPUID leaf 0x4 contains all the information. We need to
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iterate over it. */
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unsigned int eax;
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unsigned int ebx;
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unsigned int ecx;
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unsigned int edx;
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unsigned int round = 0;
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while (1)
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{
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__cpuid_count (4, round, eax, ebx, ecx, edx);
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enum { null = 0, data = 1, inst = 2, uni = 3 } type = eax & 0x1f;
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if (type == null)
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/* That was the end. */
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break;
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unsigned int level = (eax >> 5) & 0x7;
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if ((level == 1 && type == data
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&& folded_rel_name == M(_SC_LEVEL1_DCACHE_SIZE))
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|| (level == 1 && type == inst
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&& folded_rel_name == M(_SC_LEVEL1_ICACHE_SIZE))
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|| (level == 2 && folded_rel_name == M(_SC_LEVEL2_CACHE_SIZE))
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|| (level == 3 && folded_rel_name == M(_SC_LEVEL3_CACHE_SIZE))
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|| (level == 4 && folded_rel_name == M(_SC_LEVEL4_CACHE_SIZE)))
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{
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unsigned int offset = M(name) - folded_rel_name;
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if (offset == 0)
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/* Cache size. */
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return (((ebx >> 22) + 1)
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* (((ebx >> 12) & 0x3ff) + 1)
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* ((ebx & 0xfff) + 1)
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* (ecx + 1));
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if (offset == 1)
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return (ebx >> 22) + 1;
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assert (offset == 2);
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return (ebx & 0xfff) + 1;
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}
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++round;
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}
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/* There is no other cache information anywhere else. */
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break;
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}
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else
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{
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if (byte == 0x49 && folded_rel_name == M(_SC_LEVEL3_CACHE_SIZE))
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{
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/* Intel reused this value. For family 15, model 6 it
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specifies the 3rd level cache. Otherwise the 2nd
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level cache. */
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unsigned int family = cpu_features->basic.family;
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unsigned int model = cpu_features->basic.model;
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if (family == 15 && model == 6)
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{
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/* The level 3 cache is encoded for this model like
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the level 2 cache is for other models. Pretend
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the caller asked for the level 2 cache. */
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name = (_SC_LEVEL2_CACHE_SIZE
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+ (name - _SC_LEVEL3_CACHE_SIZE));
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folded_rel_name = M(_SC_LEVEL2_CACHE_SIZE);
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}
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}
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struct intel_02_cache_info *found;
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struct intel_02_cache_info search;
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search.idx = byte;
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found = bsearch (&search, intel_02_known, nintel_02_known,
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sizeof (intel_02_known[0]), intel_02_known_compare);
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if (found != NULL)
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{
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if (found->rel_name == folded_rel_name)
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{
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unsigned int offset = M(name) - folded_rel_name;
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if (offset == 0)
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/* Cache size. */
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return found->size;
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if (offset == 1)
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return found->assoc;
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assert (offset == 2);
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return found->linesize;
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}
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if (found->rel_name == M(_SC_LEVEL2_CACHE_SIZE))
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*has_level_2 = true;
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}
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}
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/* Next byte for the next round. */
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value >>= 8;
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}
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/* Nothing found. */
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return 0;
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}
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static long int __attribute__ ((noinline))
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handle_intel (int name, const struct cpu_features *cpu_features)
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{
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unsigned int maxidx = cpu_features->basic.max_cpuid;
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/* Return -1 for older CPUs. */
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if (maxidx < 2)
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return -1;
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/* OK, we can use the CPUID instruction to get all info about the
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caches. */
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unsigned int cnt = 0;
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unsigned int max = 1;
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long int result = 0;
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bool no_level_2_or_3 = false;
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bool has_level_2 = false;
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while (cnt++ < max)
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{
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unsigned int eax;
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unsigned int ebx;
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unsigned int ecx;
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unsigned int edx;
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__cpuid (2, eax, ebx, ecx, edx);
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/* The low byte of EAX in the first round contain the number of
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rounds we have to make. At least one, the one we are already
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doing. */
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if (cnt == 1)
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{
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max = eax & 0xff;
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eax &= 0xffffff00;
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}
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/* Process the individual registers' value. */
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result = intel_check_word (name, eax, &has_level_2,
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&no_level_2_or_3, cpu_features);
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if (result != 0)
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return result;
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result = intel_check_word (name, ebx, &has_level_2,
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&no_level_2_or_3, cpu_features);
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if (result != 0)
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return result;
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result = intel_check_word (name, ecx, &has_level_2,
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&no_level_2_or_3, cpu_features);
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if (result != 0)
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return result;
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result = intel_check_word (name, edx, &has_level_2,
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&no_level_2_or_3, cpu_features);
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if (result != 0)
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return result;
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}
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if (name >= _SC_LEVEL2_CACHE_SIZE && name <= _SC_LEVEL3_CACHE_LINESIZE
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&& no_level_2_or_3)
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return -1;
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return 0;
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}
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static long int __attribute__ ((noinline))
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2023-02-09 13:56:21 +00:00
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handle_amd (int name)
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2020-07-04 13:35:49 +00:00
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{
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unsigned int eax;
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unsigned int ebx;
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unsigned int ecx;
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unsigned int edx;
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2023-01-18 17:29:04 +00:00
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unsigned int count = 0x1;
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2020-07-04 13:35:49 +00:00
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/* No level 4 cache (yet). */
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if (name > _SC_LEVEL3_CACHE_LINESIZE)
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return 0;
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2023-01-18 17:29:04 +00:00
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if (name >= _SC_LEVEL3_CACHE_SIZE)
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count = 0x3;
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else if (name >= _SC_LEVEL2_CACHE_SIZE)
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|
|
|
count = 0x2;
|
|
|
|
else if (name >= _SC_LEVEL1_DCACHE_SIZE)
|
|
|
|
count = 0x0;
|
2020-07-04 13:35:49 +00:00
|
|
|
|
2023-01-18 17:29:04 +00:00
|
|
|
__cpuid_count (0x8000001D, count, eax, ebx, ecx, edx);
|
2020-07-04 13:35:49 +00:00
|
|
|
|
|
|
|
switch (name)
|
|
|
|
{
|
2023-02-09 13:56:21 +00:00
|
|
|
case _SC_LEVEL1_ICACHE_ASSOC:
|
|
|
|
case _SC_LEVEL1_DCACHE_ASSOC:
|
|
|
|
case _SC_LEVEL2_CACHE_ASSOC:
|
|
|
|
case _SC_LEVEL3_CACHE_ASSOC:
|
|
|
|
return ecx ? ((ebx >> 22) & 0x3ff) + 1 : 0;
|
|
|
|
case _SC_LEVEL1_ICACHE_LINESIZE:
|
|
|
|
case _SC_LEVEL1_DCACHE_LINESIZE:
|
|
|
|
case _SC_LEVEL2_CACHE_LINESIZE:
|
|
|
|
case _SC_LEVEL3_CACHE_LINESIZE:
|
|
|
|
return ecx ? (ebx & 0xfff) + 1 : 0;
|
|
|
|
case _SC_LEVEL1_ICACHE_SIZE:
|
|
|
|
case _SC_LEVEL1_DCACHE_SIZE:
|
|
|
|
case _SC_LEVEL2_CACHE_SIZE:
|
|
|
|
case _SC_LEVEL3_CACHE_SIZE:
|
|
|
|
return ecx ? (((ebx >> 22) & 0x3ff) + 1) * ((ebx & 0xfff) + 1) * (ecx + 1): 0;
|
|
|
|
default:
|
|
|
|
__builtin_unreachable ();
|
2020-07-04 13:35:49 +00:00
|
|
|
}
|
|
|
|
return -1;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
static long int __attribute__ ((noinline))
|
|
|
|
handle_zhaoxin (int name)
|
|
|
|
{
|
|
|
|
unsigned int eax;
|
|
|
|
unsigned int ebx;
|
|
|
|
unsigned int ecx;
|
|
|
|
unsigned int edx;
|
|
|
|
|
|
|
|
int folded_rel_name = (M(name) / 3) * 3;
|
|
|
|
|
|
|
|
unsigned int round = 0;
|
|
|
|
while (1)
|
|
|
|
{
|
|
|
|
__cpuid_count (4, round, eax, ebx, ecx, edx);
|
|
|
|
|
|
|
|
enum { null = 0, data = 1, inst = 2, uni = 3 } type = eax & 0x1f;
|
|
|
|
if (type == null)
|
|
|
|
break;
|
|
|
|
|
|
|
|
unsigned int level = (eax >> 5) & 0x7;
|
|
|
|
|
|
|
|
if ((level == 1 && type == data
|
|
|
|
&& folded_rel_name == M(_SC_LEVEL1_DCACHE_SIZE))
|
|
|
|
|| (level == 1 && type == inst
|
|
|
|
&& folded_rel_name == M(_SC_LEVEL1_ICACHE_SIZE))
|
|
|
|
|| (level == 2 && folded_rel_name == M(_SC_LEVEL2_CACHE_SIZE))
|
|
|
|
|| (level == 3 && folded_rel_name == M(_SC_LEVEL3_CACHE_SIZE)))
|
|
|
|
{
|
|
|
|
unsigned int offset = M(name) - folded_rel_name;
|
|
|
|
|
|
|
|
if (offset == 0)
|
|
|
|
/* Cache size. */
|
|
|
|
return (((ebx >> 22) + 1)
|
|
|
|
* (((ebx >> 12) & 0x3ff) + 1)
|
|
|
|
* ((ebx & 0xfff) + 1)
|
|
|
|
* (ecx + 1));
|
|
|
|
if (offset == 1)
|
|
|
|
return (ebx >> 22) + 1;
|
|
|
|
|
|
|
|
assert (offset == 2);
|
|
|
|
return (ebx & 0xfff) + 1;
|
|
|
|
}
|
|
|
|
|
|
|
|
++round;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Nothing found. */
|
|
|
|
return 0;
|
|
|
|
}
|
2020-09-18 14:55:14 +00:00
|
|
|
|
|
|
|
static void
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, unsigned int *threads_ptr,
|
2020-09-18 14:55:14 +00:00
|
|
|
long int core)
|
|
|
|
{
|
|
|
|
unsigned int eax;
|
|
|
|
unsigned int ebx;
|
|
|
|
unsigned int ecx;
|
|
|
|
unsigned int edx;
|
|
|
|
|
|
|
|
/* Number of logical processors sharing L2 cache. */
|
|
|
|
int threads_l2;
|
|
|
|
|
|
|
|
/* Number of logical processors sharing L3 cache. */
|
|
|
|
int threads_l3;
|
|
|
|
|
|
|
|
const struct cpu_features *cpu_features = __get_cpu_features ();
|
|
|
|
int max_cpuid = cpu_features->basic.max_cpuid;
|
|
|
|
unsigned int family = cpu_features->basic.family;
|
|
|
|
unsigned int model = cpu_features->basic.model;
|
|
|
|
long int shared = *shared_ptr;
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
long int shared_per_thread = *shared_per_thread_ptr;
|
2020-09-18 14:55:14 +00:00
|
|
|
unsigned int threads = *threads_ptr;
|
|
|
|
bool inclusive_cache = true;
|
|
|
|
bool support_count_mask = true;
|
|
|
|
|
|
|
|
/* Try L3 first. */
|
|
|
|
unsigned int level = 3;
|
|
|
|
|
|
|
|
if (cpu_features->basic.kind == arch_kind_zhaoxin && family == 6)
|
|
|
|
support_count_mask = false;
|
|
|
|
|
|
|
|
if (shared <= 0)
|
|
|
|
{
|
|
|
|
/* Try L2 otherwise. */
|
|
|
|
level = 2;
|
|
|
|
shared = core;
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
shared_per_thread = core;
|
2020-09-18 14:55:14 +00:00
|
|
|
threads_l2 = 0;
|
|
|
|
threads_l3 = -1;
|
|
|
|
}
|
|
|
|
else
|
|
|
|
{
|
|
|
|
threads_l2 = 0;
|
|
|
|
threads_l3 = 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* A value of 0 for the HTT bit indicates there is only a single
|
|
|
|
logical processor. */
|
|
|
|
if (HAS_CPU_FEATURE (HTT))
|
|
|
|
{
|
|
|
|
/* Figure out the number of logical threads that share the
|
|
|
|
highest cache level. */
|
|
|
|
if (max_cpuid >= 4)
|
|
|
|
{
|
|
|
|
int i = 0;
|
|
|
|
|
|
|
|
/* Query until cache level 2 and 3 are enumerated. */
|
|
|
|
int check = 0x1 | (threads_l3 == 0) << 1;
|
|
|
|
do
|
|
|
|
{
|
|
|
|
__cpuid_count (4, i++, eax, ebx, ecx, edx);
|
|
|
|
|
|
|
|
/* There seems to be a bug in at least some Pentium Ds
|
|
|
|
which sometimes fail to iterate all cache parameters.
|
|
|
|
Do not loop indefinitely here, stop in this case and
|
|
|
|
assume there is no such information. */
|
|
|
|
if (cpu_features->basic.kind == arch_kind_intel
|
|
|
|
&& (eax & 0x1f) == 0 )
|
|
|
|
goto intel_bug_no_cache_info;
|
|
|
|
|
|
|
|
switch ((eax >> 5) & 0x7)
|
|
|
|
{
|
|
|
|
default:
|
|
|
|
break;
|
|
|
|
case 2:
|
|
|
|
if ((check & 0x1))
|
|
|
|
{
|
|
|
|
/* Get maximum number of logical processors
|
|
|
|
sharing L2 cache. */
|
|
|
|
threads_l2 = (eax >> 14) & 0x3ff;
|
|
|
|
check &= ~0x1;
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
case 3:
|
|
|
|
if ((check & (0x1 << 1)))
|
|
|
|
{
|
|
|
|
/* Get maximum number of logical processors
|
|
|
|
sharing L3 cache. */
|
|
|
|
threads_l3 = (eax >> 14) & 0x3ff;
|
|
|
|
|
|
|
|
/* Check if L2 and L3 caches are inclusive. */
|
|
|
|
inclusive_cache = (edx & 0x2) != 0;
|
|
|
|
check &= ~(0x1 << 1);
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
while (check);
|
|
|
|
|
|
|
|
/* If max_cpuid >= 11, THREADS_L2/THREADS_L3 are the maximum
|
|
|
|
numbers of addressable IDs for logical processors sharing
|
|
|
|
the cache, instead of the maximum number of threads
|
|
|
|
sharing the cache. */
|
|
|
|
if (max_cpuid >= 11 && support_count_mask)
|
|
|
|
{
|
|
|
|
/* Find the number of logical processors shipped in
|
|
|
|
one core and apply count mask. */
|
|
|
|
i = 0;
|
|
|
|
|
|
|
|
/* Count SMT only if there is L3 cache. Always count
|
|
|
|
core if there is no L3 cache. */
|
|
|
|
int count = ((threads_l2 > 0 && level == 3)
|
|
|
|
| ((threads_l3 > 0
|
|
|
|
|| (threads_l2 > 0 && level == 2)) << 1));
|
|
|
|
|
|
|
|
while (count)
|
|
|
|
{
|
|
|
|
__cpuid_count (11, i++, eax, ebx, ecx, edx);
|
|
|
|
|
|
|
|
int shipped = ebx & 0xff;
|
|
|
|
int type = ecx & 0xff00;
|
|
|
|
if (shipped == 0 || type == 0)
|
|
|
|
break;
|
|
|
|
else if (type == 0x100)
|
|
|
|
{
|
|
|
|
/* Count SMT. */
|
|
|
|
if ((count & 0x1))
|
|
|
|
{
|
|
|
|
int count_mask;
|
|
|
|
|
|
|
|
/* Compute count mask. */
|
|
|
|
asm ("bsr %1, %0"
|
|
|
|
: "=r" (count_mask) : "g" (threads_l2));
|
|
|
|
count_mask = ~(-1 << (count_mask + 1));
|
|
|
|
threads_l2 = (shipped - 1) & count_mask;
|
|
|
|
count &= ~0x1;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
else if (type == 0x200)
|
|
|
|
{
|
|
|
|
/* Count core. */
|
|
|
|
if ((count & (0x1 << 1)))
|
|
|
|
{
|
|
|
|
int count_mask;
|
|
|
|
int threads_core
|
|
|
|
= (level == 2 ? threads_l2 : threads_l3);
|
|
|
|
|
|
|
|
/* Compute count mask. */
|
|
|
|
asm ("bsr %1, %0"
|
|
|
|
: "=r" (count_mask) : "g" (threads_core));
|
|
|
|
count_mask = ~(-1 << (count_mask + 1));
|
|
|
|
threads_core = (shipped - 1) & count_mask;
|
|
|
|
if (level == 2)
|
|
|
|
threads_l2 = threads_core;
|
|
|
|
else
|
|
|
|
threads_l3 = threads_core;
|
|
|
|
count &= ~(0x1 << 1);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
if (threads_l2 > 0)
|
|
|
|
threads_l2 += 1;
|
|
|
|
if (threads_l3 > 0)
|
|
|
|
threads_l3 += 1;
|
|
|
|
if (level == 2)
|
|
|
|
{
|
|
|
|
if (threads_l2)
|
|
|
|
{
|
|
|
|
threads = threads_l2;
|
|
|
|
if (cpu_features->basic.kind == arch_kind_intel
|
|
|
|
&& threads > 2
|
|
|
|
&& family == 6)
|
|
|
|
switch (model)
|
|
|
|
{
|
|
|
|
case 0x37:
|
|
|
|
case 0x4a:
|
|
|
|
case 0x4d:
|
|
|
|
case 0x5a:
|
|
|
|
case 0x5d:
|
|
|
|
/* Silvermont has L2 cache shared by 2 cores. */
|
|
|
|
threads = 2;
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
else if (threads_l3)
|
|
|
|
threads = threads_l3;
|
|
|
|
}
|
|
|
|
else
|
|
|
|
{
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
intel_bug_no_cache_info:
|
|
|
|
/* Assume that all logical threads share the highest cache
|
|
|
|
level. */
|
|
|
|
threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
|
|
|
|
& 0xff);
|
|
|
|
|
|
|
|
/* Get per-thread size of highest level cache. */
|
|
|
|
if (shared_per_thread > 0 && threads > 0)
|
|
|
|
shared_per_thread /= threads;
|
|
|
|
}
|
2020-09-18 14:55:14 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
/* Account for non-inclusive L2 and L3 caches. */
|
|
|
|
if (!inclusive_cache)
|
|
|
|
{
|
2023-07-18 04:14:33 +00:00
|
|
|
long int core_per_thread = threads_l2 > 0 ? (core / threads_l2) : core;
|
|
|
|
shared_per_thread += core_per_thread;
|
2020-09-18 14:55:14 +00:00
|
|
|
shared += core;
|
|
|
|
}
|
|
|
|
|
|
|
|
*shared_ptr = shared;
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
*shared_per_thread_ptr = shared_per_thread;
|
2020-09-18 14:55:14 +00:00
|
|
|
*threads_ptr = threads;
|
|
|
|
}
|
|
|
|
|
|
|
|
static void
|
|
|
|
dl_init_cacheinfo (struct cpu_features *cpu_features)
|
|
|
|
{
|
|
|
|
/* Find out what brand of processor. */
|
|
|
|
long int data = -1;
|
|
|
|
long int shared = -1;
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
long int shared_per_thread = -1;
|
2021-02-02 11:42:14 +00:00
|
|
|
long int core = -1;
|
2020-09-18 14:55:14 +00:00
|
|
|
unsigned int threads = 0;
|
|
|
|
unsigned long int level1_icache_size = -1;
|
2021-03-06 18:19:32 +00:00
|
|
|
unsigned long int level1_icache_linesize = -1;
|
2020-09-18 14:55:14 +00:00
|
|
|
unsigned long int level1_dcache_size = -1;
|
|
|
|
unsigned long int level1_dcache_assoc = -1;
|
|
|
|
unsigned long int level1_dcache_linesize = -1;
|
|
|
|
unsigned long int level2_cache_size = -1;
|
|
|
|
unsigned long int level2_cache_assoc = -1;
|
|
|
|
unsigned long int level2_cache_linesize = -1;
|
|
|
|
unsigned long int level3_cache_size = -1;
|
|
|
|
unsigned long int level3_cache_assoc = -1;
|
|
|
|
unsigned long int level3_cache_linesize = -1;
|
|
|
|
unsigned long int level4_cache_size = -1;
|
|
|
|
|
|
|
|
if (cpu_features->basic.kind == arch_kind_intel)
|
|
|
|
{
|
|
|
|
data = handle_intel (_SC_LEVEL1_DCACHE_SIZE, cpu_features);
|
|
|
|
core = handle_intel (_SC_LEVEL2_CACHE_SIZE, cpu_features);
|
|
|
|
shared = handle_intel (_SC_LEVEL3_CACHE_SIZE, cpu_features);
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
shared_per_thread = shared;
|
2020-09-18 14:55:14 +00:00
|
|
|
|
|
|
|
level1_icache_size
|
|
|
|
= handle_intel (_SC_LEVEL1_ICACHE_SIZE, cpu_features);
|
2021-03-06 18:19:32 +00:00
|
|
|
level1_icache_linesize
|
|
|
|
= handle_intel (_SC_LEVEL1_ICACHE_LINESIZE, cpu_features);
|
2020-09-18 14:55:14 +00:00
|
|
|
level1_dcache_size = data;
|
|
|
|
level1_dcache_assoc
|
|
|
|
= handle_intel (_SC_LEVEL1_DCACHE_ASSOC, cpu_features);
|
|
|
|
level1_dcache_linesize
|
|
|
|
= handle_intel (_SC_LEVEL1_DCACHE_LINESIZE, cpu_features);
|
|
|
|
level2_cache_size = core;
|
|
|
|
level2_cache_assoc
|
|
|
|
= handle_intel (_SC_LEVEL2_CACHE_ASSOC, cpu_features);
|
|
|
|
level2_cache_linesize
|
|
|
|
= handle_intel (_SC_LEVEL2_CACHE_LINESIZE, cpu_features);
|
|
|
|
level3_cache_size = shared;
|
|
|
|
level3_cache_assoc
|
|
|
|
= handle_intel (_SC_LEVEL3_CACHE_ASSOC, cpu_features);
|
|
|
|
level3_cache_linesize
|
|
|
|
= handle_intel (_SC_LEVEL3_CACHE_LINESIZE, cpu_features);
|
|
|
|
level4_cache_size
|
|
|
|
= handle_intel (_SC_LEVEL4_CACHE_SIZE, cpu_features);
|
|
|
|
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
get_common_cache_info (&shared, &shared_per_thread, &threads, core);
|
2020-09-18 14:55:14 +00:00
|
|
|
}
|
|
|
|
else if (cpu_features->basic.kind == arch_kind_zhaoxin)
|
|
|
|
{
|
|
|
|
data = handle_zhaoxin (_SC_LEVEL1_DCACHE_SIZE);
|
|
|
|
core = handle_zhaoxin (_SC_LEVEL2_CACHE_SIZE);
|
|
|
|
shared = handle_zhaoxin (_SC_LEVEL3_CACHE_SIZE);
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
shared_per_thread = shared;
|
2020-09-18 14:55:14 +00:00
|
|
|
|
|
|
|
level1_icache_size = handle_zhaoxin (_SC_LEVEL1_ICACHE_SIZE);
|
2021-03-06 18:19:32 +00:00
|
|
|
level1_icache_linesize = handle_zhaoxin (_SC_LEVEL1_ICACHE_LINESIZE);
|
2020-09-18 14:55:14 +00:00
|
|
|
level1_dcache_size = data;
|
|
|
|
level1_dcache_assoc = handle_zhaoxin (_SC_LEVEL1_DCACHE_ASSOC);
|
|
|
|
level1_dcache_linesize = handle_zhaoxin (_SC_LEVEL1_DCACHE_LINESIZE);
|
|
|
|
level2_cache_size = core;
|
|
|
|
level2_cache_assoc = handle_zhaoxin (_SC_LEVEL2_CACHE_ASSOC);
|
|
|
|
level2_cache_linesize = handle_zhaoxin (_SC_LEVEL2_CACHE_LINESIZE);
|
|
|
|
level3_cache_size = shared;
|
|
|
|
level3_cache_assoc = handle_zhaoxin (_SC_LEVEL3_CACHE_ASSOC);
|
|
|
|
level3_cache_linesize = handle_zhaoxin (_SC_LEVEL3_CACHE_LINESIZE);
|
|
|
|
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
get_common_cache_info (&shared, &shared_per_thread, &threads, core);
|
2020-09-18 14:55:14 +00:00
|
|
|
}
|
|
|
|
else if (cpu_features->basic.kind == arch_kind_amd)
|
|
|
|
{
|
2023-02-09 13:56:21 +00:00
|
|
|
data = handle_amd (_SC_LEVEL1_DCACHE_SIZE);
|
|
|
|
core = handle_amd (_SC_LEVEL2_CACHE_SIZE);
|
|
|
|
shared = handle_amd (_SC_LEVEL3_CACHE_SIZE);
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
shared_per_thread = shared;
|
2020-09-18 14:55:14 +00:00
|
|
|
|
2023-02-09 13:56:21 +00:00
|
|
|
level1_icache_size = handle_amd (_SC_LEVEL1_ICACHE_SIZE);
|
|
|
|
level1_icache_linesize = handle_amd (_SC_LEVEL1_ICACHE_LINESIZE);
|
2020-09-18 14:55:14 +00:00
|
|
|
level1_dcache_size = data;
|
2023-02-09 13:56:21 +00:00
|
|
|
level1_dcache_assoc = handle_amd (_SC_LEVEL1_DCACHE_ASSOC);
|
|
|
|
level1_dcache_linesize = handle_amd (_SC_LEVEL1_DCACHE_LINESIZE);
|
2020-09-18 14:55:14 +00:00
|
|
|
level2_cache_size = core;
|
2023-02-09 13:56:21 +00:00
|
|
|
level2_cache_assoc = handle_amd (_SC_LEVEL2_CACHE_ASSOC);
|
|
|
|
level2_cache_linesize = handle_amd (_SC_LEVEL2_CACHE_LINESIZE);
|
2020-09-18 14:55:14 +00:00
|
|
|
level3_cache_size = shared;
|
2023-02-09 13:56:21 +00:00
|
|
|
level3_cache_assoc = handle_amd (_SC_LEVEL3_CACHE_ASSOC);
|
|
|
|
level3_cache_linesize = handle_amd (_SC_LEVEL3_CACHE_LINESIZE);
|
2020-09-18 14:55:14 +00:00
|
|
|
|
|
|
|
if (shared <= 0)
|
2023-01-18 17:29:04 +00:00
|
|
|
/* No shared L3 cache. All we have is the L2 cache. */
|
2023-02-09 13:56:21 +00:00
|
|
|
shared = core;
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
|
|
|
|
if (shared_per_thread <= 0)
|
|
|
|
shared_per_thread = shared;
|
2020-09-18 14:55:14 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
cpu_features->level1_icache_size = level1_icache_size;
|
2021-03-06 18:19:32 +00:00
|
|
|
cpu_features->level1_icache_linesize = level1_icache_linesize;
|
2020-09-18 14:55:14 +00:00
|
|
|
cpu_features->level1_dcache_size = level1_dcache_size;
|
|
|
|
cpu_features->level1_dcache_assoc = level1_dcache_assoc;
|
|
|
|
cpu_features->level1_dcache_linesize = level1_dcache_linesize;
|
|
|
|
cpu_features->level2_cache_size = level2_cache_size;
|
|
|
|
cpu_features->level2_cache_assoc = level2_cache_assoc;
|
|
|
|
cpu_features->level2_cache_linesize = level2_cache_linesize;
|
|
|
|
cpu_features->level3_cache_size = level3_cache_size;
|
|
|
|
cpu_features->level3_cache_assoc = level3_cache_assoc;
|
|
|
|
cpu_features->level3_cache_linesize = level3_cache_linesize;
|
|
|
|
cpu_features->level4_cache_size = level4_cache_size;
|
|
|
|
|
2023-06-07 18:18:03 +00:00
|
|
|
unsigned long int cachesize_non_temporal_divisor
|
|
|
|
= cpu_features->cachesize_non_temporal_divisor;
|
|
|
|
if (cachesize_non_temporal_divisor <= 0)
|
|
|
|
cachesize_non_temporal_divisor = 4;
|
|
|
|
|
|
|
|
/* The default setting for the non_temporal threshold is [1/8, 1/2] of size
|
|
|
|
of the chip's cache (depending on `cachesize_non_temporal_divisor` which
|
2023-06-19 21:58:33 +00:00
|
|
|
is microarch specific. The default is 1/4). For most Intel and AMD
|
2023-06-07 18:18:03 +00:00
|
|
|
processors with an initial release date between 2017 and 2023, a thread's
|
|
|
|
typical share of the cache is from 18-64MB. Using a reasonable size
|
|
|
|
fraction of L3 is meant to estimate the point where non-temporal stores
|
|
|
|
begin out-competing REP MOVSB. As well the point where the fact that
|
|
|
|
non-temporal stores are forced back to main memory would already occurred
|
|
|
|
to the majority of the lines in the copy. Note, concerns about the entire
|
|
|
|
L3 cache being evicted by the copy are mostly alleviated by the fact that
|
|
|
|
modern HW detects streaming patterns and provides proper LRU hints so that
|
|
|
|
the maximum thrashing capped at 1/associativity. */
|
|
|
|
unsigned long int non_temporal_threshold
|
|
|
|
= shared / cachesize_non_temporal_divisor;
|
x86: Increase `non_temporal_threshold` to roughly `sizeof_L3 / 4`
Current `non_temporal_threshold` set to roughly '3/4 * sizeof_L3 /
ncores_per_socket'. This patch updates that value to roughly
'sizeof_L3 / 4`
The original value (specifically dividing the `ncores_per_socket`) was
done to limit the amount of other threads' data a `memcpy`/`memset`
could evict.
Dividing by 'ncores_per_socket', however leads to exceedingly low
non-temporal thresholds and leads to using non-temporal stores in
cases where REP MOVSB is multiple times faster.
Furthermore, non-temporal stores are written directly to main memory
so using it at a size much smaller than L3 can place soon to be
accessed data much further away than it otherwise could be. As well,
modern machines are able to detect streaming patterns (especially if
REP MOVSB is used) and provide LRU hints to the memory subsystem. This
in affect caps the total amount of eviction at 1/cache_associativity,
far below meaningfully thrashing the entire cache.
As best I can tell, the benchmarks that lead this small threshold
where done comparing non-temporal stores versus standard cacheable
stores. A better comparison (linked below) is to be REP MOVSB which,
on the measure systems, is nearly 2x faster than non-temporal stores
at the low-end of the previous threshold, and within 10% for over
100MB copies (well past even the current threshold). In cases with a
low number of threads competing for bandwidth, REP MOVSB is ~2x faster
up to `sizeof_L3`.
The divisor of `4` is a somewhat arbitrary value. From benchmarks it
seems Skylake and Icelake both prefer a divisor of `2`, but older CPUs
such as Broadwell prefer something closer to `8`. This patch is meant
to be followed up by another one to make the divisor cpu-specific, but
in the meantime (and for easier backporting), this patch settles on
`4` as a middle-ground.
Benchmarks comparing non-temporal stores, REP MOVSB, and cacheable
stores where done using:
https://github.com/goldsteinn/memcpy-nt-benchmarks
Sheets results (also available in pdf on the github):
https://docs.google.com/spreadsheets/d/e/2PACX-1vS183r0rW_jRX6tG_E90m9qVuFiMbRIJvi5VAE8yYOvEOIEEc3aSNuEsrFbuXw5c3nGboxMmrupZD7K/pubhtml
Reviewed-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2023-06-07 18:18:01 +00:00
|
|
|
/* If no ERMS, we use the per-thread L3 chunking. Normal cacheable stores run
|
|
|
|
a higher risk of actually thrashing the cache as they don't have a HW LRU
|
|
|
|
hint. As well, their performance in highly parallel situations is
|
|
|
|
noticeably worse. */
|
|
|
|
if (!CPU_FEATURE_USABLE_P (cpu_features, ERMS))
|
|
|
|
non_temporal_threshold = shared_per_thread * 3 / 4;
|
2023-01-03 21:06:48 +00:00
|
|
|
/* SIZE_MAX >> 4 because memmove-vec-unaligned-erms right-shifts the value of
|
|
|
|
'x86_non_temporal_threshold' by `LOG_4X_MEMCPY_THRESH` (4) and it is best
|
|
|
|
if that operation cannot overflow. Minimum of 0x4040 (16448) because the
|
|
|
|
L(large_memset_4x) loops need 64-byte to cache align and enough space for
|
|
|
|
at least 1 iteration of 4x PAGE_SIZE unrolled loop. Both values are
|
|
|
|
reflected in the manual. */
|
|
|
|
unsigned long int maximum_non_temporal_threshold = SIZE_MAX >> 4;
|
|
|
|
unsigned long int minimum_non_temporal_threshold = 0x4040;
|
2023-05-09 03:10:20 +00:00
|
|
|
|
|
|
|
/* If `non_temporal_threshold` less than `minimum_non_temporal_threshold`
|
|
|
|
it most likely means we failed to detect the cache info. We don't want
|
|
|
|
to default to `minimum_non_temporal_threshold` as such a small value,
|
|
|
|
while correct, has bad performance. We default to 64MB as reasonable
|
|
|
|
default bound. 64MB is likely conservative in that most/all systems would
|
|
|
|
choose a lower value so it should never forcing non-temporal stores when
|
|
|
|
they otherwise wouldn't be used. */
|
2023-01-03 21:06:48 +00:00
|
|
|
if (non_temporal_threshold < minimum_non_temporal_threshold)
|
2023-05-09 03:10:20 +00:00
|
|
|
non_temporal_threshold = 64 * 1024 * 1024;
|
2023-01-03 21:06:48 +00:00
|
|
|
else if (non_temporal_threshold > maximum_non_temporal_threshold)
|
|
|
|
non_temporal_threshold = maximum_non_temporal_threshold;
|
2020-09-18 14:55:14 +00:00
|
|
|
|
|
|
|
/* NB: The REP MOVSB threshold must be greater than VEC_SIZE * 8. */
|
|
|
|
unsigned int minimum_rep_movsb_threshold;
|
x86: Double size of ERMS rep_movsb_threshold in dl-cacheinfo.h
No bug.
This patch doubles the rep_movsb_threshold when using ERMS. Based on
benchmarks the vector copy loop, especially now that it handles 4k
aliasing, is better for these medium ranged.
On Skylake with ERMS:
Size, Align1, Align2, dst>src,(rep movsb) / (vec copy)
4096, 0, 0, 0, 0.975
4096, 0, 0, 1, 0.953
4096, 12, 0, 0, 0.969
4096, 12, 0, 1, 0.872
4096, 44, 0, 0, 0.979
4096, 44, 0, 1, 0.83
4096, 0, 12, 0, 1.006
4096, 0, 12, 1, 0.989
4096, 0, 44, 0, 0.739
4096, 0, 44, 1, 0.942
4096, 12, 12, 0, 1.009
4096, 12, 12, 1, 0.973
4096, 44, 44, 0, 0.791
4096, 44, 44, 1, 0.961
4096, 2048, 0, 0, 0.978
4096, 2048, 0, 1, 0.951
4096, 2060, 0, 0, 0.986
4096, 2060, 0, 1, 0.963
4096, 2048, 12, 0, 0.971
4096, 2048, 12, 1, 0.941
4096, 2060, 12, 0, 0.977
4096, 2060, 12, 1, 0.949
8192, 0, 0, 0, 0.85
8192, 0, 0, 1, 0.845
8192, 13, 0, 0, 0.937
8192, 13, 0, 1, 0.939
8192, 45, 0, 0, 0.932
8192, 45, 0, 1, 0.927
8192, 0, 13, 0, 0.621
8192, 0, 13, 1, 0.62
8192, 0, 45, 0, 0.53
8192, 0, 45, 1, 0.516
8192, 13, 13, 0, 0.664
8192, 13, 13, 1, 0.659
8192, 45, 45, 0, 0.593
8192, 45, 45, 1, 0.575
8192, 2048, 0, 0, 0.854
8192, 2048, 0, 1, 0.834
8192, 2061, 0, 0, 0.863
8192, 2061, 0, 1, 0.857
8192, 2048, 13, 0, 0.63
8192, 2048, 13, 1, 0.629
8192, 2061, 13, 0, 0.627
8192, 2061, 13, 1, 0.62
Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
2021-11-01 05:49:52 +00:00
|
|
|
/* NB: The default REP MOVSB threshold is 4096 * (VEC_SIZE / 16) for
|
|
|
|
VEC_SIZE == 64 or 32. For VEC_SIZE == 16, the default REP MOVSB
|
|
|
|
threshold is 2048 * (VEC_SIZE / 16). */
|
2020-09-18 14:55:14 +00:00
|
|
|
unsigned int rep_movsb_threshold;
|
|
|
|
if (CPU_FEATURE_USABLE_P (cpu_features, AVX512F)
|
|
|
|
&& !CPU_FEATURE_PREFERRED_P (cpu_features, Prefer_No_AVX512))
|
|
|
|
{
|
x86: Double size of ERMS rep_movsb_threshold in dl-cacheinfo.h
No bug.
This patch doubles the rep_movsb_threshold when using ERMS. Based on
benchmarks the vector copy loop, especially now that it handles 4k
aliasing, is better for these medium ranged.
On Skylake with ERMS:
Size, Align1, Align2, dst>src,(rep movsb) / (vec copy)
4096, 0, 0, 0, 0.975
4096, 0, 0, 1, 0.953
4096, 12, 0, 0, 0.969
4096, 12, 0, 1, 0.872
4096, 44, 0, 0, 0.979
4096, 44, 0, 1, 0.83
4096, 0, 12, 0, 1.006
4096, 0, 12, 1, 0.989
4096, 0, 44, 0, 0.739
4096, 0, 44, 1, 0.942
4096, 12, 12, 0, 1.009
4096, 12, 12, 1, 0.973
4096, 44, 44, 0, 0.791
4096, 44, 44, 1, 0.961
4096, 2048, 0, 0, 0.978
4096, 2048, 0, 1, 0.951
4096, 2060, 0, 0, 0.986
4096, 2060, 0, 1, 0.963
4096, 2048, 12, 0, 0.971
4096, 2048, 12, 1, 0.941
4096, 2060, 12, 0, 0.977
4096, 2060, 12, 1, 0.949
8192, 0, 0, 0, 0.85
8192, 0, 0, 1, 0.845
8192, 13, 0, 0, 0.937
8192, 13, 0, 1, 0.939
8192, 45, 0, 0, 0.932
8192, 45, 0, 1, 0.927
8192, 0, 13, 0, 0.621
8192, 0, 13, 1, 0.62
8192, 0, 45, 0, 0.53
8192, 0, 45, 1, 0.516
8192, 13, 13, 0, 0.664
8192, 13, 13, 1, 0.659
8192, 45, 45, 0, 0.593
8192, 45, 45, 1, 0.575
8192, 2048, 0, 0, 0.854
8192, 2048, 0, 1, 0.834
8192, 2061, 0, 0, 0.863
8192, 2061, 0, 1, 0.857
8192, 2048, 13, 0, 0.63
8192, 2048, 13, 1, 0.629
8192, 2061, 13, 0, 0.627
8192, 2061, 13, 1, 0.62
Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
2021-11-01 05:49:52 +00:00
|
|
|
rep_movsb_threshold = 4096 * (64 / 16);
|
2020-09-18 14:55:14 +00:00
|
|
|
minimum_rep_movsb_threshold = 64 * 8;
|
|
|
|
}
|
|
|
|
else if (CPU_FEATURE_PREFERRED_P (cpu_features,
|
|
|
|
AVX_Fast_Unaligned_Load))
|
|
|
|
{
|
x86: Double size of ERMS rep_movsb_threshold in dl-cacheinfo.h
No bug.
This patch doubles the rep_movsb_threshold when using ERMS. Based on
benchmarks the vector copy loop, especially now that it handles 4k
aliasing, is better for these medium ranged.
On Skylake with ERMS:
Size, Align1, Align2, dst>src,(rep movsb) / (vec copy)
4096, 0, 0, 0, 0.975
4096, 0, 0, 1, 0.953
4096, 12, 0, 0, 0.969
4096, 12, 0, 1, 0.872
4096, 44, 0, 0, 0.979
4096, 44, 0, 1, 0.83
4096, 0, 12, 0, 1.006
4096, 0, 12, 1, 0.989
4096, 0, 44, 0, 0.739
4096, 0, 44, 1, 0.942
4096, 12, 12, 0, 1.009
4096, 12, 12, 1, 0.973
4096, 44, 44, 0, 0.791
4096, 44, 44, 1, 0.961
4096, 2048, 0, 0, 0.978
4096, 2048, 0, 1, 0.951
4096, 2060, 0, 0, 0.986
4096, 2060, 0, 1, 0.963
4096, 2048, 12, 0, 0.971
4096, 2048, 12, 1, 0.941
4096, 2060, 12, 0, 0.977
4096, 2060, 12, 1, 0.949
8192, 0, 0, 0, 0.85
8192, 0, 0, 1, 0.845
8192, 13, 0, 0, 0.937
8192, 13, 0, 1, 0.939
8192, 45, 0, 0, 0.932
8192, 45, 0, 1, 0.927
8192, 0, 13, 0, 0.621
8192, 0, 13, 1, 0.62
8192, 0, 45, 0, 0.53
8192, 0, 45, 1, 0.516
8192, 13, 13, 0, 0.664
8192, 13, 13, 1, 0.659
8192, 45, 45, 0, 0.593
8192, 45, 45, 1, 0.575
8192, 2048, 0, 0, 0.854
8192, 2048, 0, 1, 0.834
8192, 2061, 0, 0, 0.863
8192, 2061, 0, 1, 0.857
8192, 2048, 13, 0, 0.63
8192, 2048, 13, 1, 0.629
8192, 2061, 13, 0, 0.627
8192, 2061, 13, 1, 0.62
Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
2021-11-01 05:49:52 +00:00
|
|
|
rep_movsb_threshold = 4096 * (32 / 16);
|
2020-09-18 14:55:14 +00:00
|
|
|
minimum_rep_movsb_threshold = 32 * 8;
|
|
|
|
}
|
|
|
|
else
|
|
|
|
{
|
|
|
|
rep_movsb_threshold = 2048 * (16 / 16);
|
|
|
|
minimum_rep_movsb_threshold = 16 * 8;
|
|
|
|
}
|
x86: Set rep_movsb_threshold to 2112 on processors with FSRM
The glibc memcpy benchmark on Intel Core i7-1065G7 (Ice Lake) showed
that REP MOVSB became faster after 2112 bytes:
Vector Move REP MOVSB
length=2112, align1=0, align2=0: 24.20 24.40
length=2112, align1=1, align2=0: 26.07 23.13
length=2112, align1=0, align2=1: 27.18 28.13
length=2112, align1=1, align2=1: 26.23 25.16
length=2176, align1=0, align2=0: 23.18 22.52
length=2176, align1=2, align2=0: 25.45 22.52
length=2176, align1=0, align2=2: 27.14 27.82
length=2176, align1=2, align2=2: 22.73 25.56
length=2240, align1=0, align2=0: 24.62 24.25
length=2240, align1=3, align2=0: 29.77 27.15
length=2240, align1=0, align2=3: 35.55 29.93
length=2240, align1=3, align2=3: 34.49 25.15
length=2304, align1=0, align2=0: 34.75 26.64
length=2304, align1=4, align2=0: 32.09 22.63
length=2304, align1=0, align2=4: 28.43 31.24
Use REP MOVSB for data size > 2112 bytes in memcpy on processors with
fast short REP MOVSB (FSRM).
* sysdeps/x86/dl-cacheinfo.h (dl_init_cacheinfo): Set
rep_movsb_threshold to 2112 on processors with fast short REP
MOVSB (FSRM).
2021-04-30 12:58:59 +00:00
|
|
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/* NB: The default REP MOVSB threshold is 2112 on processors with fast
|
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short REP MOVSB (FSRM). */
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if (CPU_FEATURE_USABLE_P (cpu_features, FSRM))
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rep_movsb_threshold = 2112;
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2020-09-18 14:55:14 +00:00
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/* The default threshold to use Enhanced REP STOSB. */
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unsigned long int rep_stosb_threshold = 2048;
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long int tunable_size;
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tunable_size = TUNABLE_GET (x86_data_cache_size, long int, NULL);
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/* NB: Ignore the default value 0. */
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if (tunable_size != 0)
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data = tunable_size;
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tunable_size = TUNABLE_GET (x86_shared_cache_size, long int, NULL);
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/* NB: Ignore the default value 0. */
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if (tunable_size != 0)
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shared = tunable_size;
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tunable_size = TUNABLE_GET (x86_non_temporal_threshold, long int, NULL);
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2023-01-03 21:06:48 +00:00
|
|
|
if (tunable_size > minimum_non_temporal_threshold
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|
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&& tunable_size <= maximum_non_temporal_threshold)
|
2020-09-18 14:55:14 +00:00
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|
non_temporal_threshold = tunable_size;
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tunable_size = TUNABLE_GET (x86_rep_movsb_threshold, long int, NULL);
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if (tunable_size > minimum_rep_movsb_threshold)
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|
|
rep_movsb_threshold = tunable_size;
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|
|
|
/* NB: The default value of the x86_rep_stosb_threshold tunable is the
|
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|
|
same as the default value of __x86_rep_stosb_threshold and the
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|
|
minimum value is fixed. */
|
|
|
|
rep_stosb_threshold = TUNABLE_GET (x86_rep_stosb_threshold,
|
|
|
|
long int, NULL);
|
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|
|
|
2021-02-03 14:33:19 +00:00
|
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|
TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, data, 0, SIZE_MAX);
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TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, shared, 0, SIZE_MAX);
|
2021-02-05 07:48:58 +00:00
|
|
|
TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, non_temporal_threshold,
|
2023-01-03 21:06:48 +00:00
|
|
|
minimum_non_temporal_threshold,
|
|
|
|
maximum_non_temporal_threshold);
|
2021-02-05 07:48:58 +00:00
|
|
|
TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, rep_movsb_threshold,
|
2021-02-03 14:33:19 +00:00
|
|
|
minimum_rep_movsb_threshold, SIZE_MAX);
|
2021-02-05 07:48:58 +00:00
|
|
|
TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1,
|
2021-02-03 14:33:19 +00:00
|
|
|
SIZE_MAX);
|
2020-09-18 14:55:14 +00:00
|
|
|
|
2022-06-14 20:50:11 +00:00
|
|
|
unsigned long int rep_movsb_stop_threshold;
|
|
|
|
/* ERMS feature is implemented from AMD Zen3 architecture and it is
|
|
|
|
performing poorly for data above L2 cache size. Henceforth, adding
|
|
|
|
an upper bound threshold parameter to limit the usage of Enhanced
|
|
|
|
REP MOVSB operations and setting its value to L2 cache size. */
|
|
|
|
if (cpu_features->basic.kind == arch_kind_amd)
|
|
|
|
rep_movsb_stop_threshold = core;
|
|
|
|
/* Setting the upper bound of ERMS to the computed value of
|
|
|
|
non-temporal threshold for architectures other than AMD. */
|
|
|
|
else
|
|
|
|
rep_movsb_stop_threshold = non_temporal_threshold;
|
|
|
|
|
2020-09-18 14:55:14 +00:00
|
|
|
cpu_features->data_cache_size = data;
|
|
|
|
cpu_features->shared_cache_size = shared;
|
|
|
|
cpu_features->non_temporal_threshold = non_temporal_threshold;
|
|
|
|
cpu_features->rep_movsb_threshold = rep_movsb_threshold;
|
|
|
|
cpu_features->rep_stosb_threshold = rep_stosb_threshold;
|
2021-02-02 11:42:14 +00:00
|
|
|
cpu_features->rep_movsb_stop_threshold = rep_movsb_stop_threshold;
|
2020-09-18 14:55:14 +00:00
|
|
|
}
|