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x86: Optimizing memcpy for AMD Zen architecture.

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Modifying the shareable cache '__x86_shared_cache_size', which is a
factor in computing the non-temporal threshold parameter
'__x86_shared_non_temporal_threshold' to optimize memcpy for AMD Zen
architectures.
In the existing implementation, the shareable cache is computed as 'L3
per thread, L2 per core'. Recomputing this shareable cache as 'L3 per
CCX(Core-Complex)' has brought in performance gains.
As per the large bench variant results, this patch also addresses the
regression problem on AMD Zen architectures.

Backport of commit 59803e81f9 upstream,
with the fix from cb3a749a22 ("x86:
Restore processing of cache size tunables in init_cacheinfo") applied.

Reviewed-by: Premachandra Mallappa <premachandra.mallappa@amd.com>
Co-Authored-by: Florian Weimer <fweimer@redhat.com>
This commit is contained in:
Sajan Karumanchi 2020-10-28 13:05:33 +05:30 committed by Florian Weimer
parent 8d730cb25a
commit 48cf525f4b
1 changed files with 17 additions and 3 deletions
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16
sysdeps/x86/cacheinfo.c
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@ -722,7 +722,7 @@ intel_bug_no_cache_info:
threads = 1 << ((ecx >> 12) & 0x0f);
}
if (threads == 0)
if (threads == 0 || cpu_features->basic.family >= 0x17)
{
/* If APIC ID width is not available, use logical
processor count. */
@ -737,9 +737,23 @@ intel_bug_no_cache_info:
if (threads > 0)
shared /= threads;
/* Get shared cache per ccx for Zen architectures. */
if (cpu_features->basic.family >= 0x17)
{
unsigned int eax;
/* Get number of threads share the L3 cache in CCX. */
__cpuid_count (0x8000001D, 0x3, eax, ebx, ecx, edx);
unsigned int threads_per_ccx = ((eax >> 14) & 0xfff) + 1;
shared *= threads_per_ccx;
}
else
{
/* Account for exclusive L2 and L3 caches. */
shared += core;
}
}
#ifndef DISABLE_PREFETCHW
if (max_cpuid_ex >= 0x80000001)