| Message ID | 20240813185714.2999710-2-goldstein.w.n@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | x86: Add `Avoid_STOSB` tunable to allow NT memset without ERMS | expand |
On Tue, Aug 13, 2024 at 11:57 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote: > > The goal of this flag is to allow targets which don't prefer/have ERMS > to still access the non-temporal memset implementation. > > There are 4 cases for tuning memset: > 1) `Avoid_STOSB && Avoid_Non_Temporal_Memset` > - Memset with temporal stores > 2) `Avoid_STOSB && !Avoid_Non_Temporal_Memset` > - Memset with temporal/non-temporal stores. Non-temporal path > goes through `rep stosb` path. We accomplish this by setting > `x86_rep_stosb_threshold` to > `x86_memset_non_temporal_threshold`. > 3) `!Avoid_STOSB && Avoid_Non_Temporal_Memset` > - Memset with temporal stores/`rep stosb` > 3) `!Avoid_STOSB && !Avoid_Non_Temporal_Memset` > - Memset with temporal stores/`rep stosb`/non-temporal stores. > --- > sysdeps/x86/cpu-features.c | 4 +++ > sysdeps/x86/cpu-tunables.c | 2 ++ > sysdeps/x86/dl-cacheinfo.h | 34 ++++++++++++++++--- > ...cpu-features-preferred_feature_index_1.def | 1 + > sysdeps/x86/tst-hwcap-tunables.c | 6 ++-- > sysdeps/x86_64/multiarch/ifunc-memset.h | 19 ++++++++--- > 6 files changed, 54 insertions(+), 12 deletions(-) > > diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c > index a4786d23c7..15c4ab24a5 100644 > --- a/sysdeps/x86/cpu-features.c > +++ b/sysdeps/x86/cpu-features.c > @@ -1119,6 +1119,10 @@ https://www.intel.com/content/www/us/en/support/articles/000059422/processors.ht > if (CPU_FEATURES_CPU_P (cpu_features, CMOV)) > cpu_features->preferred[index_arch_I686] |= bit_arch_I686; > > + /* No ERMS, we want to avoid stosb for memset. */ > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) The comment doesn't match the code. Did you mean if (!CPU_FEATURE_USABLE_P (cpu_features, ERMS)) ^ > + cpu_features->preferred[index_arch_Avoid_STOSB] |= bit_arch_Avoid_STOSB; > + > #if !HAS_CPUID > no_cpuid: > #endif > diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c > index ccc6b64dc2..cd36de2d8b 100644 > --- a/sysdeps/x86/cpu-tunables.c > +++ b/sysdeps/x86/cpu-tunables.c > @@ -193,6 +193,8 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp) > 11); > CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Prefer_FSRM, > 11); > + CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Avoid_STOSB, > + 11); > CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH (n, cpu_features, > Slow_SSE4_2, > SSE4_2, > diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h > index 3d0c8d43b8..82e4aa5c19 100644 > --- a/sysdeps/x86/dl-cacheinfo.h > +++ b/sysdeps/x86/dl-cacheinfo.h > @@ -1041,18 +1041,42 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) > slightly better than ERMS. */ > rep_stosb_threshold = SIZE_MAX; > > + /* > + For memset, the non-temporal implementation is only accessed through the > + stosb code. ie: > + ``` > + if (size >= rep_stosb_thresh) > + { > + if (size >= non_temporal_thresh) > + { > + do_non_temporal (); > + } > + do_stosb (); > + } > + do_normal_vec_loop (); > + ``` > + So if we prefer non-temporal, set `rep_stosb_thresh = non_temporal_thresh` > + to enable the implementation. If `rep_stosb_thresh = non_temporal_thresh`, > + `rep stosb` will never be used. > + */ > + TUNABLE_SET_WITH_BOUNDS (x86_memset_non_temporal_threshold, > + memset_non_temporal_threshold, > + minimum_non_temporal_threshold, SIZE_MAX); > + /* Do `rep_stosb_thresh = non_temporal_thresh` after setting/getting the > + final value of `x86_memset_non_temporal_threshold`. In some cases this can > + be a matter of correctness. */ > + if (CPU_FEATURES_ARCH_P (cpu_features, Avoid_STOSB)) > + rep_stosb_threshold > + = TUNABLE_GET (x86_memset_non_temporal_threshold, long int, NULL); > + TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1, > + SIZE_MAX); > TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, data, 0, SIZE_MAX); > TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, shared, 0, SIZE_MAX); > TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, non_temporal_threshold, > minimum_non_temporal_threshold, > maximum_non_temporal_threshold); > - TUNABLE_SET_WITH_BOUNDS (x86_memset_non_temporal_threshold, > - memset_non_temporal_threshold, > - minimum_non_temporal_threshold, SIZE_MAX); > TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, rep_movsb_threshold, > minimum_rep_movsb_threshold, SIZE_MAX); > - TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1, > - SIZE_MAX); > > unsigned long int rep_movsb_stop_threshold; > /* Setting the upper bound of ERMS to the computed value of > diff --git a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def > index 61bbbc2e89..2a58000147 100644 > --- a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def > +++ b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def > @@ -34,3 +34,4 @@ BIT (MathVec_Prefer_No_AVX512) > BIT (Prefer_FSRM) > BIT (Avoid_Short_Distance_REP_MOVSB) > BIT (Avoid_Non_Temporal_Memset) > +BIT (Avoid_STOSB) > diff --git a/sysdeps/x86/tst-hwcap-tunables.c b/sysdeps/x86/tst-hwcap-tunables.c > index 94307283d7..1920f5057e 100644 > --- a/sysdeps/x86/tst-hwcap-tunables.c > +++ b/sysdeps/x86/tst-hwcap-tunables.c > @@ -60,7 +60,8 @@ static const struct test_t > /* Disable everything. */ > "-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX512F,-AVX512VL," > "-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,-ERMS," > - "-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset", > + "-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset," > + "-Avoid_STOSB", > test_1, > array_length (test_1) > }, > @@ -68,7 +69,8 @@ static const struct test_t > /* Same as before, but with some empty suboptions. */ > ",-,-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX512F,-AVX512VL," > "-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,,-," > - "-ERMS,-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset,-,", > + "-ERMS,-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset," > + "-Avoid_STOSB,-,", > test_1, > array_length (test_1) > } > diff --git a/sysdeps/x86_64/multiarch/ifunc-memset.h b/sysdeps/x86_64/multiarch/ifunc-memset.h > index 7a637ef7ca..2f8ae661f8 100644 > --- a/sysdeps/x86_64/multiarch/ifunc-memset.h > +++ b/sysdeps/x86_64/multiarch/ifunc-memset.h > @@ -61,7 +61,9 @@ IFUNC_SELECTOR (void) > && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW) > && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)) > { > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > + || !CPU_FEATURES_ARCH_P (cpu_features, > + Avoid_Non_Temporal_Memset)) Please create an inline function instead of duplicating the logic. > return OPTIMIZE (avx512_unaligned_erms); > > return OPTIMIZE (avx512_unaligned); > @@ -76,7 +78,9 @@ IFUNC_SELECTOR (void) > && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW) > && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)) > { > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > + || !CPU_FEATURES_ARCH_P (cpu_features, > + Avoid_Non_Temporal_Memset)) > return OPTIMIZE (evex_unaligned_erms); > > return OPTIMIZE (evex_unaligned); > @@ -84,7 +88,9 @@ IFUNC_SELECTOR (void) > > if (CPU_FEATURE_USABLE_P (cpu_features, RTM)) > { > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > + || !CPU_FEATURES_ARCH_P (cpu_features, > + Avoid_Non_Temporal_Memset)) > return OPTIMIZE (avx2_unaligned_erms_rtm); > > return OPTIMIZE (avx2_unaligned_rtm); > @@ -93,14 +99,17 @@ IFUNC_SELECTOR (void) > if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features, > Prefer_No_VZEROUPPER, !)) > { > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > + || !CPU_FEATURES_ARCH_P (cpu_features, > + Avoid_Non_Temporal_Memset)) > return OPTIMIZE (avx2_unaligned_erms); > > return OPTIMIZE (avx2_unaligned); > } > } > > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > + || !CPU_FEATURES_ARCH_P (cpu_features, Avoid_Non_Temporal_Memset)) > return OPTIMIZE (sse2_unaligned_erms); > > return OPTIMIZE (sse2_unaligned); > -- > 2.34.1 >
On Wed, Aug 14, 2024 at 3:20 AM H.J. Lu <hjl.tools@gmail.com> wrote: > > On Tue, Aug 13, 2024 at 11:57 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote: > > > > The goal of this flag is to allow targets which don't prefer/have ERMS > > to still access the non-temporal memset implementation. > > > > There are 4 cases for tuning memset: > > 1) `Avoid_STOSB && Avoid_Non_Temporal_Memset` > > - Memset with temporal stores > > 2) `Avoid_STOSB && !Avoid_Non_Temporal_Memset` > > - Memset with temporal/non-temporal stores. Non-temporal path > > goes through `rep stosb` path. We accomplish this by setting > > `x86_rep_stosb_threshold` to > > `x86_memset_non_temporal_threshold`. > > 3) `!Avoid_STOSB && Avoid_Non_Temporal_Memset` > > - Memset with temporal stores/`rep stosb` > > 3) `!Avoid_STOSB && !Avoid_Non_Temporal_Memset` > > - Memset with temporal stores/`rep stosb`/non-temporal stores. > > --- > > sysdeps/x86/cpu-features.c | 4 +++ > > sysdeps/x86/cpu-tunables.c | 2 ++ > > sysdeps/x86/dl-cacheinfo.h | 34 ++++++++++++++++--- > > ...cpu-features-preferred_feature_index_1.def | 1 + > > sysdeps/x86/tst-hwcap-tunables.c | 6 ++-- > > sysdeps/x86_64/multiarch/ifunc-memset.h | 19 ++++++++--- > > 6 files changed, 54 insertions(+), 12 deletions(-) > > > > diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c > > index a4786d23c7..15c4ab24a5 100644 > > --- a/sysdeps/x86/cpu-features.c > > +++ b/sysdeps/x86/cpu-features.c > > @@ -1119,6 +1119,10 @@ https://www.intel.com/content/www/us/en/support/articles/000059422/processors.ht > > if (CPU_FEATURES_CPU_P (cpu_features, CMOV)) > > cpu_features->preferred[index_arch_I686] |= bit_arch_I686; > > > > + /* No ERMS, we want to avoid stosb for memset. */ > > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > > The comment doesn't match the code. Did you mean > > if (!CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > ^ > Yes. Its already fixed in v2. > > + cpu_features->preferred[index_arch_Avoid_STOSB] |= bit_arch_Avoid_STOSB; > > + > > #if !HAS_CPUID > > no_cpuid: > > #endif > > diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c > > index ccc6b64dc2..cd36de2d8b 100644 > > --- a/sysdeps/x86/cpu-tunables.c > > +++ b/sysdeps/x86/cpu-tunables.c > > @@ -193,6 +193,8 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp) > > 11); > > CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Prefer_FSRM, > > 11); > > + CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Avoid_STOSB, > > + 11); > > CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH (n, cpu_features, > > Slow_SSE4_2, > > SSE4_2, > > diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h > > index 3d0c8d43b8..82e4aa5c19 100644 > > --- a/sysdeps/x86/dl-cacheinfo.h > > +++ b/sysdeps/x86/dl-cacheinfo.h > > @@ -1041,18 +1041,42 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) > > slightly better than ERMS. */ > > rep_stosb_threshold = SIZE_MAX; > > > > + /* > > + For memset, the non-temporal implementation is only accessed through the > > + stosb code. ie: > > + ``` > > + if (size >= rep_stosb_thresh) > > + { > > + if (size >= non_temporal_thresh) > > + { > > + do_non_temporal (); > > + } > > + do_stosb (); > > + } > > + do_normal_vec_loop (); > > + ``` > > + So if we prefer non-temporal, set `rep_stosb_thresh = non_temporal_thresh` > > + to enable the implementation. If `rep_stosb_thresh = non_temporal_thresh`, > > + `rep stosb` will never be used. > > + */ > > + TUNABLE_SET_WITH_BOUNDS (x86_memset_non_temporal_threshold, > > + memset_non_temporal_threshold, > > + minimum_non_temporal_threshold, SIZE_MAX); > > + /* Do `rep_stosb_thresh = non_temporal_thresh` after setting/getting the > > + final value of `x86_memset_non_temporal_threshold`. In some cases this can > > + be a matter of correctness. */ > > + if (CPU_FEATURES_ARCH_P (cpu_features, Avoid_STOSB)) > > + rep_stosb_threshold > > + = TUNABLE_GET (x86_memset_non_temporal_threshold, long int, NULL); > > + TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1, > > + SIZE_MAX); > > TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, data, 0, SIZE_MAX); > > TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, shared, 0, SIZE_MAX); > > TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, non_temporal_threshold, > > minimum_non_temporal_threshold, > > maximum_non_temporal_threshold); > > - TUNABLE_SET_WITH_BOUNDS (x86_memset_non_temporal_threshold, > > - memset_non_temporal_threshold, > > - minimum_non_temporal_threshold, SIZE_MAX); > > TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, rep_movsb_threshold, > > minimum_rep_movsb_threshold, SIZE_MAX); > > - TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1, > > - SIZE_MAX); > > > > unsigned long int rep_movsb_stop_threshold; > > /* Setting the upper bound of ERMS to the computed value of > > diff --git a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def > > index 61bbbc2e89..2a58000147 100644 > > --- a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def > > +++ b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def > > @@ -34,3 +34,4 @@ BIT (MathVec_Prefer_No_AVX512) > > BIT (Prefer_FSRM) > > BIT (Avoid_Short_Distance_REP_MOVSB) > > BIT (Avoid_Non_Temporal_Memset) > > +BIT (Avoid_STOSB) > > diff --git a/sysdeps/x86/tst-hwcap-tunables.c b/sysdeps/x86/tst-hwcap-tunables.c > > index 94307283d7..1920f5057e 100644 > > --- a/sysdeps/x86/tst-hwcap-tunables.c > > +++ b/sysdeps/x86/tst-hwcap-tunables.c > > @@ -60,7 +60,8 @@ static const struct test_t > > /* Disable everything. */ > > "-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX512F,-AVX512VL," > > "-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,-ERMS," > > - "-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset", > > + "-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset," > > + "-Avoid_STOSB", > > test_1, > > array_length (test_1) > > }, > > @@ -68,7 +69,8 @@ static const struct test_t > > /* Same as before, but with some empty suboptions. */ > > ",-,-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX512F,-AVX512VL," > > "-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,,-," > > - "-ERMS,-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset,-,", > > + "-ERMS,-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset," > > + "-Avoid_STOSB,-,", > > test_1, > > array_length (test_1) > > } > > diff --git a/sysdeps/x86_64/multiarch/ifunc-memset.h b/sysdeps/x86_64/multiarch/ifunc-memset.h > > index 7a637ef7ca..2f8ae661f8 100644 > > --- a/sysdeps/x86_64/multiarch/ifunc-memset.h > > +++ b/sysdeps/x86_64/multiarch/ifunc-memset.h > > @@ -61,7 +61,9 @@ IFUNC_SELECTOR (void) > > && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW) > > && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)) > > { > > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > > + || !CPU_FEATURES_ARCH_P (cpu_features, > > + Avoid_Non_Temporal_Memset)) > > Please create an inline function instead of duplicating the logic. > Done. > > return OPTIMIZE (avx512_unaligned_erms); > > > > return OPTIMIZE (avx512_unaligned); > > @@ -76,7 +78,9 @@ IFUNC_SELECTOR (void) > > && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW) > > && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)) > > { > > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > > + || !CPU_FEATURES_ARCH_P (cpu_features, > > + Avoid_Non_Temporal_Memset)) > > return OPTIMIZE (evex_unaligned_erms); > > > > return OPTIMIZE (evex_unaligned); > > @@ -84,7 +88,9 @@ IFUNC_SELECTOR (void) > > > > if (CPU_FEATURE_USABLE_P (cpu_features, RTM)) > > { > > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > > + || !CPU_FEATURES_ARCH_P (cpu_features, > > + Avoid_Non_Temporal_Memset)) > > return OPTIMIZE (avx2_unaligned_erms_rtm); > > > > return OPTIMIZE (avx2_unaligned_rtm); > > @@ -93,14 +99,17 @@ IFUNC_SELECTOR (void) > > if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features, > > Prefer_No_VZEROUPPER, !)) > > { > > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > > + || !CPU_FEATURES_ARCH_P (cpu_features, > > + Avoid_Non_Temporal_Memset)) > > return OPTIMIZE (avx2_unaligned_erms); > > > > return OPTIMIZE (avx2_unaligned); > > } > > } > > > > - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) > > + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) > > + || !CPU_FEATURES_ARCH_P (cpu_features, Avoid_Non_Temporal_Memset)) > > return OPTIMIZE (sse2_unaligned_erms); > > > > return OPTIMIZE (sse2_unaligned); > > -- > > 2.34.1 > > > > > -- > H.J.
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c index a4786d23c7..15c4ab24a5 100644 --- a/sysdeps/x86/cpu-features.c +++ b/sysdeps/x86/cpu-features.c @@ -1119,6 +1119,10 @@ https://www.intel.com/content/www/us/en/support/articles/000059422/processors.ht if (CPU_FEATURES_CPU_P (cpu_features, CMOV)) cpu_features->preferred[index_arch_I686] |= bit_arch_I686; + /* No ERMS, we want to avoid stosb for memset. */ + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) + cpu_features->preferred[index_arch_Avoid_STOSB] |= bit_arch_Avoid_STOSB; + #if !HAS_CPUID no_cpuid: #endif diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c index ccc6b64dc2..cd36de2d8b 100644 --- a/sysdeps/x86/cpu-tunables.c +++ b/sysdeps/x86/cpu-tunables.c @@ -193,6 +193,8 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp) 11); CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Prefer_FSRM, 11); + CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Avoid_STOSB, + 11); CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH (n, cpu_features, Slow_SSE4_2, SSE4_2, diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h index 3d0c8d43b8..82e4aa5c19 100644 --- a/sysdeps/x86/dl-cacheinfo.h +++ b/sysdeps/x86/dl-cacheinfo.h @@ -1041,18 +1041,42 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) slightly better than ERMS. */ rep_stosb_threshold = SIZE_MAX; + /* + For memset, the non-temporal implementation is only accessed through the + stosb code. ie: + ``` + if (size >= rep_stosb_thresh) + { + if (size >= non_temporal_thresh) + { + do_non_temporal (); + } + do_stosb (); + } + do_normal_vec_loop (); + ``` + So if we prefer non-temporal, set `rep_stosb_thresh = non_temporal_thresh` + to enable the implementation. If `rep_stosb_thresh = non_temporal_thresh`, + `rep stosb` will never be used. + */ + TUNABLE_SET_WITH_BOUNDS (x86_memset_non_temporal_threshold, + memset_non_temporal_threshold, + minimum_non_temporal_threshold, SIZE_MAX); + /* Do `rep_stosb_thresh = non_temporal_thresh` after setting/getting the + final value of `x86_memset_non_temporal_threshold`. In some cases this can + be a matter of correctness. */ + if (CPU_FEATURES_ARCH_P (cpu_features, Avoid_STOSB)) + rep_stosb_threshold + = TUNABLE_GET (x86_memset_non_temporal_threshold, long int, NULL); + TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1, + SIZE_MAX); TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, data, 0, SIZE_MAX); TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, shared, 0, SIZE_MAX); TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, non_temporal_threshold, minimum_non_temporal_threshold, maximum_non_temporal_threshold); - TUNABLE_SET_WITH_BOUNDS (x86_memset_non_temporal_threshold, - memset_non_temporal_threshold, - minimum_non_temporal_threshold, SIZE_MAX); TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, rep_movsb_threshold, minimum_rep_movsb_threshold, SIZE_MAX); - TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1, - SIZE_MAX); unsigned long int rep_movsb_stop_threshold; /* Setting the upper bound of ERMS to the computed value of diff --git a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def index 61bbbc2e89..2a58000147 100644 --- a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def +++ b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def @@ -34,3 +34,4 @@ BIT (MathVec_Prefer_No_AVX512) BIT (Prefer_FSRM) BIT (Avoid_Short_Distance_REP_MOVSB) BIT (Avoid_Non_Temporal_Memset) +BIT (Avoid_STOSB) diff --git a/sysdeps/x86/tst-hwcap-tunables.c b/sysdeps/x86/tst-hwcap-tunables.c index 94307283d7..1920f5057e 100644 --- a/sysdeps/x86/tst-hwcap-tunables.c +++ b/sysdeps/x86/tst-hwcap-tunables.c @@ -60,7 +60,8 @@ static const struct test_t /* Disable everything. */ "-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX512F,-AVX512VL," "-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,-ERMS," - "-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset", + "-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset," + "-Avoid_STOSB", test_1, array_length (test_1) }, @@ -68,7 +69,8 @@ static const struct test_t /* Same as before, but with some empty suboptions. */ ",-,-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX512F,-AVX512VL," "-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,,-," - "-ERMS,-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset,-,", + "-ERMS,-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset," + "-Avoid_STOSB,-,", test_1, array_length (test_1) } diff --git a/sysdeps/x86_64/multiarch/ifunc-memset.h b/sysdeps/x86_64/multiarch/ifunc-memset.h index 7a637ef7ca..2f8ae661f8 100644 --- a/sysdeps/x86_64/multiarch/ifunc-memset.h +++ b/sysdeps/x86_64/multiarch/ifunc-memset.h @@ -61,7 +61,9 @@ IFUNC_SELECTOR (void) && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW) && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)) { - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) + || !CPU_FEATURES_ARCH_P (cpu_features, + Avoid_Non_Temporal_Memset)) return OPTIMIZE (avx512_unaligned_erms); return OPTIMIZE (avx512_unaligned); @@ -76,7 +78,9 @@ IFUNC_SELECTOR (void) && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW) && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)) { - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) + || !CPU_FEATURES_ARCH_P (cpu_features, + Avoid_Non_Temporal_Memset)) return OPTIMIZE (evex_unaligned_erms); return OPTIMIZE (evex_unaligned); @@ -84,7 +88,9 @@ IFUNC_SELECTOR (void) if (CPU_FEATURE_USABLE_P (cpu_features, RTM)) { - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) + || !CPU_FEATURES_ARCH_P (cpu_features, + Avoid_Non_Temporal_Memset)) return OPTIMIZE (avx2_unaligned_erms_rtm); return OPTIMIZE (avx2_unaligned_rtm); @@ -93,14 +99,17 @@ IFUNC_SELECTOR (void) if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_VZEROUPPER, !)) { - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) + || !CPU_FEATURES_ARCH_P (cpu_features, + Avoid_Non_Temporal_Memset)) return OPTIMIZE (avx2_unaligned_erms); return OPTIMIZE (avx2_unaligned); } } - if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)) + if (CPU_FEATURE_USABLE_P (cpu_features, ERMS) + || !CPU_FEATURES_ARCH_P (cpu_features, Avoid_Non_Temporal_Memset)) return OPTIMIZE (sse2_unaligned_erms); return OPTIMIZE (sse2_unaligned);
The goal of this flag is to allow targets which don't prefer/have ERMS to still access the non-temporal memset implementation. There are 4 cases for tuning memset: 1) `Avoid_STOSB && Avoid_Non_Temporal_Memset` - Memset with temporal stores 2) `Avoid_STOSB && !Avoid_Non_Temporal_Memset` - Memset with temporal/non-temporal stores. Non-temporal path goes through `rep stosb` path. We accomplish this by setting `x86_rep_stosb_threshold` to `x86_memset_non_temporal_threshold`. 3) `!Avoid_STOSB && Avoid_Non_Temporal_Memset` - Memset with temporal stores/`rep stosb` 3) `!Avoid_STOSB && !Avoid_Non_Temporal_Memset` - Memset with temporal stores/`rep stosb`/non-temporal stores. --- sysdeps/x86/cpu-features.c | 4 +++ sysdeps/x86/cpu-tunables.c | 2 ++ sysdeps/x86/dl-cacheinfo.h | 34 ++++++++++++++++--- ...cpu-features-preferred_feature_index_1.def | 1 + sysdeps/x86/tst-hwcap-tunables.c | 6 ++-- sysdeps/x86_64/multiarch/ifunc-memset.h | 19 ++++++++--- 6 files changed, 54 insertions(+), 12 deletions(-)