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This benchmark is an attempt to eliminate cache effects from string benchmarks. The benchmark walks both ways through a large memory area and copies different sizes of memory and alignments one at a time instead of looping around in the same memory area. This is a good metric to have alongside the other memcpy benchmarks, especially for larger sizes where the likelihood of the call being done only once is pretty high. * benchtests/bench-memcpy-walk.c: New file. * benchtests/Makefile (string-benchset): Add it.
128 lines
3.8 KiB
C
128 lines
3.8 KiB
C
/* Measure memcpy function combined throughput for different alignments.
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Copyright (C) 2017 Free Software Foundation, Inc.
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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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<http://www.gnu.org/licenses/>. */
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/* This microbenchmark measures the throughput of memcpy for various sizes from
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1 byte to 32MiB, doubling every iteration and then misaligning by 0-15
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bytes. The copies are done from source to destination and then back and the
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source walks forward across the array and the destination walks backward by
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one byte each, thus measuring misaligned accesses as well. The idea is to
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avoid caching effects by copying a different string and far enough from each
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other, walking in different directions so that we can measure prefetcher
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efficiency (software or hardware) more closely than with a loop copying the
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same data over and over, which eventually only gives us L1 cache
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performance. */
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#ifndef MEMCPY_RESULT
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# define MEMCPY_RESULT(dst, len) dst
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# define START_SIZE 1
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# define MIN_PAGE_SIZE (getpagesize () + 32 * 1024 * 1024)
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# define TEST_MAIN
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# define TEST_NAME "memcpy"
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# define TIMEOUT (20 * 60)
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# include "bench-string.h"
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IMPL (memcpy, 1)
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#endif
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#include "json-lib.h"
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typedef char *(*proto_t) (char *, const char *, size_t);
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static void
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do_one_test (json_ctx_t *json_ctx, impl_t *impl, char *dst, char *src,
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size_t len)
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{
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size_t i, iters = MIN_PAGE_SIZE / len;
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timing_t start, stop, cur;
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char *dst_end = dst + MIN_PAGE_SIZE - len;
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char *src_end = src + MIN_PAGE_SIZE - len;
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TIMING_NOW (start);
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/* Copy the entire buffer back and forth, LEN at a time. */
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for (i = 0; i < iters && dst_end >= dst && src <= src_end; src++, dst_end--)
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{
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CALL (impl, dst_end, src, len);
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CALL (impl, src, dst_end, len);
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i += 2;
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}
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TIMING_NOW (stop);
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TIMING_DIFF (cur, start, stop);
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/* Get time taken per function call. */
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json_element_double (json_ctx, (double) cur * len / i);
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}
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static void
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do_test (json_ctx_t *json_ctx, size_t len)
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{
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json_element_object_begin (json_ctx);
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json_attr_uint (json_ctx, "length", (double) len);
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json_array_begin (json_ctx, "timings");
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FOR_EACH_IMPL (impl, 0)
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do_one_test (json_ctx, impl, (char *) buf2, (char *) buf1, len);
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json_array_end (json_ctx);
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json_element_object_end (json_ctx);
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}
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int
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test_main (void)
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{
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json_ctx_t json_ctx;
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size_t i;
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test_init ();
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json_init (&json_ctx, 0, stdout);
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json_document_begin (&json_ctx);
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json_attr_string (&json_ctx, "timing_type", TIMING_TYPE);
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json_attr_object_begin (&json_ctx, "functions");
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json_attr_object_begin (&json_ctx, "memcpy");
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json_attr_string (&json_ctx, "bench-variant", "walk");
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json_array_begin (&json_ctx, "ifuncs");
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FOR_EACH_IMPL (impl, 0)
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json_element_string (&json_ctx, impl->name);
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json_array_end (&json_ctx);
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json_array_begin (&json_ctx, "results");
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for (i = START_SIZE; i <= MIN_PAGE_SIZE; i <<= 1)
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{
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/* Test length alignments from 0-16 bytes. */
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for (int j = 0; j < 8; j++)
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{
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do_test (&json_ctx, i + j);
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do_test (&json_ctx, i + 16 - j);
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}
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}
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json_array_end (&json_ctx);
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json_attr_object_end (&json_ctx);
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json_attr_object_end (&json_ctx);
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json_document_end (&json_ctx);
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return ret;
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}
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#include <support/test-driver.c>
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