x86: Optimizing memcpy for AMD Zen architecture.
Commit Message
From: Sajan Karumanchi <sajan.karumanchi@amd.com>
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.
Reviewed-by: Premachandra Mallappa <premachandra.mallappa@amd.com>
---
sysdeps/x86/cacheinfo.h | 32 ++++++++++++++++++++++++++------
1 file changed, 26 insertions(+), 6 deletions(-)
Comments
* sajan karumanchi:
> From: Sajan Karumanchi <sajan.karumanchi@amd.com>
>
> 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.
>
> Reviewed-by: Premachandra Mallappa <premachandra.mallappa@amd.com>
Thanks, I've pushed this version for you.
Florian
@@ -320,7 +320,7 @@ init_cacheinfo (void)
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. */
@@ -335,13 +335,30 @@ init_cacheinfo (void)
if (threads > 0)
shared /= threads;
- /* Account for exclusive L2 and L3 caches. */
- shared += core;
- }
+ /* 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;
+ }
+ }
}
if (cpu_features->data_cache_size != 0)
- data = cpu_features->data_cache_size;
+ {
+ if (data == 0 || cpu_features->basic.kind != arch_kind_amd)
+ data = cpu_features->data_cache_size;
+ }
if (data > 0)
{
@@ -354,7 +371,10 @@ init_cacheinfo (void)
}
if (cpu_features->shared_cache_size != 0)
- shared = cpu_features->shared_cache_size;
+ {
+ if (shared == 0 || cpu_features->basic.kind != arch_kind_amd)
+ shared = cpu_features->shared_cache_size;
+ }
if (shared > 0)
{