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glibc/SOURCES/glibc-rh1817513-72.patch

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commit 3f4b61a0b8de67ef9f20737919c713ddfc4bd620
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Mon Jul 6 11:48:09 2020 -0700
x86: Add thresholds for "rep movsb/stosb" to tunables
Add x86_rep_movsb_threshold and x86_rep_stosb_threshold to tunables
to update thresholds for "rep movsb" and "rep stosb" at run-time.
Note that the user specified threshold for "rep movsb" smaller than
the minimum threshold will be ignored.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Conflicts:
sysdeps/x86/cacheinfo.c
(Previous backport of the shared cache computation fix.)
diff --git a/manual/tunables.texi b/manual/tunables.texi
index ef10d2872cfc244e..55d5dfb14db4dfb8 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -373,6 +373,22 @@ like memmove and memcpy.
This tunable is specific to i386 and x86-64.
@end deftp
+@deftp Tunable glibc.cpu.x86_rep_movsb_threshold
+The @code{glibc.cpu.x86_rep_movsb_threshold} tunable allows the user to
+set threshold in bytes to start using "rep movsb". The value must be
+greater than zero, and currently defaults to 2048 bytes.
+
+This tunable is specific to i386 and x86-64.
+@end deftp
+
+@deftp Tunable glibc.cpu.x86_rep_stosb_threshold
+The @code{glibc.cpu.x86_rep_stosb_threshold} tunable allows the user to
+set threshold in bytes to start using "rep stosb". The value must be
+greater than zero, and currently defaults to 2048 bytes.
+
+This tunable is specific to i386 and x86-64.
+@end deftp
+
@deftp Tunable glibc.cpu.x86_ibt
The @code{glibc.cpu.x86_ibt} tunable allows the user to control how
indirect branch tracking (IBT) should be enabled. Accepted values are
diff --git a/sysdeps/x86/cacheinfo.c b/sysdeps/x86/cacheinfo.c
index aa7cb705d546bcd0..c741a69fb19a1e95 100644
--- a/sysdeps/x86/cacheinfo.c
+++ b/sysdeps/x86/cacheinfo.c
@@ -530,6 +530,12 @@ long int __x86_raw_shared_cache_size attribute_hidden = 1024 * 1024;
/* Threshold to use non temporal store. */
long int __x86_shared_non_temporal_threshold attribute_hidden;
+/* Threshold to use Enhanced REP MOVSB. */
+long int __x86_rep_movsb_threshold attribute_hidden = 2048;
+
+/* Threshold to use Enhanced REP STOSB. */
+long int __x86_rep_stosb_threshold attribute_hidden = 2048;
+
#ifndef DISABLE_PREFETCHW
/* PREFETCHW support flag for use in memory and string routines. */
int __x86_prefetchw attribute_hidden;
@@ -892,6 +898,36 @@ init_cacheinfo (void)
= (cpu_features->non_temporal_threshold != 0
? cpu_features->non_temporal_threshold
: __x86_shared_cache_size * 3 / 4);
+
+ /* NB: The REP MOVSB threshold must be greater than VEC_SIZE * 8. */
+ unsigned int minimum_rep_movsb_threshold;
+ /* NB: The default REP MOVSB threshold is 2048 * (VEC_SIZE / 16). */
+ unsigned int rep_movsb_threshold;
+ if (CPU_FEATURES_ARCH_P (cpu_features, AVX512F_Usable)
+ && !CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_AVX512))
+ {
+ rep_movsb_threshold = 2048 * (64 / 16);
+ minimum_rep_movsb_threshold = 64 * 8;
+ }
+ else if (CPU_FEATURES_ARCH_P (cpu_features,
+ AVX_Fast_Unaligned_Load))
+ {
+ rep_movsb_threshold = 2048 * (32 / 16);
+ minimum_rep_movsb_threshold = 32 * 8;
+ }
+ else
+ {
+ rep_movsb_threshold = 2048 * (16 / 16);
+ minimum_rep_movsb_threshold = 16 * 8;
+ }
+ if (cpu_features->rep_movsb_threshold > minimum_rep_movsb_threshold)
+ __x86_rep_movsb_threshold = cpu_features->rep_movsb_threshold;
+ else
+ __x86_rep_movsb_threshold = rep_movsb_threshold;
+
+# if HAVE_TUNABLES
+ __x86_rep_stosb_threshold = cpu_features->rep_stosb_threshold;
+# endif
}
#endif
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index 21565474839efffc..ad470f79ef7769fc 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -605,6 +605,10 @@ no_cpuid:
TUNABLE_GET (hwcaps, tunable_val_t *, TUNABLE_CALLBACK (set_hwcaps));
cpu_features->non_temporal_threshold
= TUNABLE_GET (x86_non_temporal_threshold, long int, NULL);
+ cpu_features->rep_movsb_threshold
+ = TUNABLE_GET (x86_rep_movsb_threshold, long int, NULL);
+ cpu_features->rep_stosb_threshold
+ = TUNABLE_GET (x86_rep_stosb_threshold, long int, NULL);
cpu_features->data_cache_size
= TUNABLE_GET (x86_data_cache_size, long int, NULL);
cpu_features->shared_cache_size
diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h
index e7ea9e8ece3e8211..0f19c64352c4d7f1 100644
--- a/sysdeps/x86/cpu-features.h
+++ b/sysdeps/x86/cpu-features.h
@@ -102,6 +102,10 @@ struct cpu_features
unsigned long int shared_cache_size;
/* Threshold to use non temporal store. */
unsigned long int non_temporal_threshold;
+ /* Threshold to use "rep movsb". */
+ unsigned long int rep_movsb_threshold;
+ /* Threshold to use "rep stosb". */
+ unsigned long int rep_stosb_threshold;
};
/* Used from outside of glibc to get access to the CPU features
diff --git a/sysdeps/x86/dl-tunables.list b/sysdeps/x86/dl-tunables.list
index 2a457d0eec9c3122..e066313a1d1dd009 100644
--- a/sysdeps/x86/dl-tunables.list
+++ b/sysdeps/x86/dl-tunables.list
@@ -30,6 +30,30 @@ glibc {
x86_non_temporal_threshold {
type: SIZE_T
}
+ x86_rep_movsb_threshold {
+ type: SIZE_T
+ # Since there is overhead to set up REP MOVSB operation, REP MOVSB
+ # isn't faster on short data. The memcpy micro benchmark in glibc
+ # shows that 2KB is the approximate value above which REP MOVSB
+ # becomes faster than SSE2 optimization on processors with Enhanced
+ # REP MOVSB. Since larger register size can move more data with a
+ # single load and store, the threshold is higher with larger register
+ # size. Note: Since the REP MOVSB threshold must be greater than 8
+ # times of vector size, the minium value must be updated at run-time.
+ minval: 1
+ default: 2048
+ }
+ x86_rep_stosb_threshold {
+ type: SIZE_T
+ # Since there is overhead to set up REP STOSB operation, REP STOSB
+ # isn't faster on short data. The memset micro benchmark in glibc
+ # shows that 2KB is the approximate value above which REP STOSB
+ # becomes faster on processors with Enhanced REP STOSB. Since the
+ # stored value is fixed, larger register size has minimal impact
+ # on threshold.
+ minval: 1
+ default: 2048
+ }
x86_data_cache_size {
type: SIZE_T
}
diff --git a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
index e2ede45e9f68791b..c952576cfdf6e3e6 100644
--- a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
+++ b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
@@ -56,17 +56,6 @@
# endif
#endif
-/* Threshold to use Enhanced REP MOVSB. Since there is overhead to set
- up REP MOVSB operation, REP MOVSB isn't faster on short data. The
- memcpy micro benchmark in glibc shows that 2KB is the approximate
- value above which REP MOVSB becomes faster than SSE2 optimization
- on processors with Enhanced REP MOVSB. Since larger register size
- can move more data with a single load and store, the threshold is
- higher with larger register size. */
-#ifndef REP_MOVSB_THRESHOLD
-# define REP_MOVSB_THRESHOLD (2048 * (VEC_SIZE / 16))
-#endif
-
#ifndef PREFETCH
# define PREFETCH(addr) prefetcht0 addr
#endif
@@ -245,9 +234,6 @@ L(movsb):
leaq (%rsi,%rdx), %r9
cmpq %r9, %rdi
/* Avoid slow backward REP MOVSB. */
-# if REP_MOVSB_THRESHOLD <= (VEC_SIZE * 8)
-# error Unsupported REP_MOVSB_THRESHOLD and VEC_SIZE!
-# endif
jb L(more_8x_vec_backward)
1:
movq %rdx, %rcx
@@ -323,7 +309,7 @@ L(between_2_3):
#if defined USE_MULTIARCH && IS_IN (libc)
L(movsb_more_2x_vec):
- cmpq $REP_MOVSB_THRESHOLD, %rdx
+ cmp __x86_rep_movsb_threshold(%rip), %RDX_LP
ja L(movsb)
#endif
L(more_2x_vec):
diff --git a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
index dc9cb88b37a5477a..270a1d49b34be9f5 100644
--- a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
+++ b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
@@ -58,16 +58,6 @@
# endif
#endif
-/* Threshold to use Enhanced REP STOSB. Since there is overhead to set
- up REP STOSB operation, REP STOSB isn't faster on short data. The
- memset micro benchmark in glibc shows that 2KB is the approximate
- value above which REP STOSB becomes faster on processors with
- Enhanced REP STOSB. Since the stored value is fixed, larger register
- size has minimal impact on threshold. */
-#ifndef REP_STOSB_THRESHOLD
-# define REP_STOSB_THRESHOLD 2048
-#endif
-
#ifndef SECTION
# error SECTION is not defined!
#endif
@@ -173,7 +163,7 @@ ENTRY (MEMSET_SYMBOL (__memset, unaligned_erms))
ret
L(stosb_more_2x_vec):
- cmpq $REP_STOSB_THRESHOLD, %rdx
+ cmp __x86_rep_stosb_threshold(%rip), %RDX_LP
ja L(stosb)
#endif
L(more_2x_vec):
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