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| author | H.J. Lu <hjl.tools@gmail.com> | 2017-04-18 14:01:45 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2017-04-18 14:01:45 -0700 |
| commit | 4cb334c4d6249686653137ec273d081371b3672d (patch) | |
| tree | 0ddce19851595aeccad1caf222c91014f7817de2 /sysdeps/x86/cpu-features.c | |
| parent | 1c53cb49de6d82d9469ccbd5aa0c55924502bd8b (diff) | |
| download | glibc-4cb334c4d6249686653137ec273d081371b3672d.tar.gz glibc-4cb334c4d6249686653137ec273d081371b3672d.tar.xz glibc-4cb334c4d6249686653137ec273d081371b3672d.zip | |
x86: Use AVX2 memcpy/memset on Skylake server [BZ #21396]
On Skylake server, AVX512 load/store instructions in memcpy/memset may lead to lower CPU turbo frequency in certain situations. Use of AVX2 in memcpy/memset has been observed to have improved overall performance in many workloads due to the higher frequency. Since AVX512ER is unique to Xeon Phi, this patch sets Prefer_No_AVX512 if AVX512ER isn't available so that AVX2 versions of memcpy/memset are used on Skylake server. [BZ #21396] * sysdeps/x86/cpu-features.c (init_cpu_features): Set Prefer_No_AVX512 if AVX512ER isn't available. * sysdeps/x86/cpu-features.h (bit_arch_Prefer_No_AVX512): New. (index_arch_Prefer_No_AVX512): Likewise. * sysdeps/x86_64/multiarch/memcpy.S (__new_memcpy): Don't use AVX512 version if Prefer_No_AVX512 is set. * sysdeps/x86_64/multiarch/memcpy_chk.S (__memcpy_chk): Likewise. * sysdeps/x86_64/multiarch/memmove.S (__libc_memmove): Likewise. * sysdeps/x86_64/multiarch/memmove_chk.S (__memmove_chk): Likewise. * sysdeps/x86_64/multiarch/mempcpy.S (__mempcpy): Likewise. * sysdeps/x86_64/multiarch/mempcpy_chk.S (__mempcpy_chk): Likewise. * sysdeps/x86_64/multiarch/memset.S (memset): Likewise. * sysdeps/x86_64/multiarch/memset_chk.S (__memset_chk): Likewise.
Diffstat (limited to 'sysdeps/x86/cpu-features.c')
| -rw-r--r-- | sysdeps/x86/cpu-features.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c index ae7f844f8b..f30918dd3b 100644 --- a/sysdeps/x86/cpu-features.c +++ b/sysdeps/x86/cpu-features.c @@ -224,10 +224,14 @@ init_cpu_features (struct cpu_features *cpu_features) |= bit_arch_AVX_Fast_Unaligned_Load; /* Since AVX512ER is unique to Xeon Phi, set Prefer_No_VZEROUPPER - if AVX512ER is available. */ + if AVX512ER is available. Don't use AVX512 to avoid lower CPU + frequency if AVX512ER isn't available. */ if (CPU_FEATURES_CPU_P (cpu_features, AVX512ER)) cpu_features->feature[index_arch_Prefer_No_VZEROUPPER] |= bit_arch_Prefer_No_VZEROUPPER; + else + cpu_features->feature[index_arch_Prefer_No_AVX512] + |= bit_arch_Prefer_No_AVX512; /* To avoid SSE transition penalty, use _dl_runtime_resolve_slow. If XGETBV suports ECX == 1, use _dl_runtime_resolve_opt. */ |