From: "H.J. Lu" <hjl.tools@gmail.com>
To: libc-alpha@sourceware.org
Subject: [PATCH] x86-64: Add Avoid_Short_Distance_REP_MOVSB
Date: Mon, 26 Jul 2021 05:00:55 -0700 [thread overview]
Message-ID: <20210726120055.1089971-1-hjl.tools@gmail.com> (raw)
commit 3ec5d83d2a237d39e7fd6ef7a0bc8ac4c171a4a5
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Sat Jan 25 14:19:40 2020 -0800
x86-64: Avoid rep movsb with short distance [BZ #27130]
introduced some regressions on Intel processors without Fast Short REP
MOV (FSRM). Add Avoid_Short_Distance_REP_MOVSB to avoid rep movsb with
short distance only on Intel processors with FSRM. bench-memmove-large
on Skylake server shows that cycles of __memmove_evex_unaligned_erms are
improved for the following data size:
before after Improvement
length=4127, align1=3, align2=0: 479.38 343.00 28%
length=4223, align1=9, align2=5: 405.62 335.50 17%
length=8223, align1=3, align2=0: 786.12 495.00 37%
length=8319, align1=9, align2=5: 256.69 170.38 33%
length=16415, align1=3, align2=0: 1436.88 839.50 41%
length=16511, align1=9, align2=5: 1375.50 840.62 39%
length=32799, align1=3, align2=0: 2890.00 1850.62 36%
length=32895, align1=9, align2=5: 2891.38 1948.62 32%
There are no regression on Ice Lake server.
---
sysdeps/x86/cacheinfo.h | 7 +++++++
sysdeps/x86/cpu-features.c | 5 +++++
.../x86/include/cpu-features-preferred_feature_index_1.def | 1 +
sysdeps/x86/sysdep.h | 3 +++
sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S | 5 +++++
5 files changed, 21 insertions(+)
diff --git a/sysdeps/x86/cacheinfo.h b/sysdeps/x86/cacheinfo.h
index eba8dbc4a6..174ea38f5b 100644
--- a/sysdeps/x86/cacheinfo.h
+++ b/sysdeps/x86/cacheinfo.h
@@ -49,6 +49,9 @@ long int __x86_rep_stosb_threshold attribute_hidden = 2048;
/* Threshold to stop using Enhanced REP MOVSB. */
long int __x86_rep_movsb_stop_threshold attribute_hidden;
+/* String/memory function control. */
+int __x86_string_control attribute_hidden;
+
static void
init_cacheinfo (void)
{
@@ -71,5 +74,9 @@ init_cacheinfo (void)
__x86_rep_movsb_threshold = cpu_features->rep_movsb_threshold;
__x86_rep_stosb_threshold = cpu_features->rep_stosb_threshold;
__x86_rep_movsb_stop_threshold = cpu_features->rep_movsb_stop_threshold;
+
+ if (CPU_FEATURES_ARCH_P (cpu_features, Avoid_Short_Distance_REP_MOVSB))
+ __x86_string_control
+ |= X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB;
}
#endif
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index 706a172ba9..645bba6314 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -555,6 +555,11 @@ init_cpu_features (struct cpu_features *cpu_features)
cpu_features->preferred[index_arch_Prefer_AVX2_STRCMP]
|= bit_arch_Prefer_AVX2_STRCMP;
}
+
+ /* Avoid avoid short distance REP MOVSB on processor with FSRM. */
+ if (CPU_FEATURES_CPU_P (cpu_features, FSRM))
+ cpu_features->preferred[index_arch_Avoid_Short_Distance_REP_MOVSB]
+ |= bit_arch_Avoid_Short_Distance_REP_MOVSB;
}
/* This spells out "AuthenticAMD" or "HygonGenuine". */
else if ((ebx == 0x68747541 && ecx == 0x444d4163 && edx == 0x69746e65)
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 133aab19f1..d7c93f00c5 100644
--- a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def
+++ b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def
@@ -33,3 +33,4 @@ BIT (Prefer_No_AVX512)
BIT (MathVec_Prefer_No_AVX512)
BIT (Prefer_FSRM)
BIT (Prefer_AVX2_STRCMP)
+BIT (Avoid_Short_Distance_REP_MOVSB)
diff --git a/sysdeps/x86/sysdep.h b/sysdeps/x86/sysdep.h
index 51c069bfe1..35cb90d507 100644
--- a/sysdeps/x86/sysdep.h
+++ b/sysdeps/x86/sysdep.h
@@ -57,6 +57,9 @@ enum cf_protection_level
#define STATE_SAVE_MASK \
((1 << 1) | (1 << 2) | (1 << 3) | (1 << 5) | (1 << 6) | (1 << 7))
+/* Avoid short distance REP MOVSB. */
+#define X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB (1 << 0)
+
#ifdef __ASSEMBLER__
/* Syntactic details of assembler. */
diff --git a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
index a783da5de2..9f02624375 100644
--- a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
+++ b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
@@ -325,12 +325,16 @@ L(movsb):
/* Avoid slow backward REP MOVSB. */
jb L(more_8x_vec_backward)
# if AVOID_SHORT_DISTANCE_REP_MOVSB
+ andl $X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB, __x86_string_control(%rip)
+ jz 3f
movq %rdi, %rcx
subq %rsi, %rcx
jmp 2f
# endif
1:
# if AVOID_SHORT_DISTANCE_REP_MOVSB
+ andl $X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB, __x86_string_control(%rip)
+ jz 3f
movq %rsi, %rcx
subq %rdi, %rcx
2:
@@ -338,6 +342,7 @@ L(movsb):
is N*4GB + [1..63] with N >= 0. */
cmpl $63, %ecx
jbe L(more_2x_vec) /* Avoid "rep movsb" if ECX <= 63. */
+3:
# endif
mov %RDX_LP, %RCX_LP
rep movsb
--
2.31.1
next reply other threads:[~2021-07-26 12:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-26 12:00 H.J. Lu [this message]
2021-07-26 17:20 ` Noah Goldstein
2021-07-26 18:50 ` H.J. Lu
2021-07-27 2:15 ` Carlos O'Donell
2021-07-27 3:11 ` H.J. Lu
2021-07-27 4:05 ` Noah Goldstein
2021-07-27 16:05 ` [PATCH v2] " H.J. Lu
2021-07-27 19:12 ` Noah Goldstein
2021-07-27 19:22 ` [PATCH v3] " H.J. Lu
2021-07-27 19:50 ` Noah Goldstein
2021-07-27 19:55 ` H.J. Lu
2021-07-28 15:08 ` H.J. Lu
2021-08-28 0:27 ` [PATCH] " Alexey Tourbin
2021-08-28 2:57 ` Noah Goldstein
2022-04-28 0:15 ` Sunil Pandey
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