From: "H.J. Lu" <hjl.tools@gmail.com>
To: libc-alpha@sourceware.org
Subject: [PATCH] x86: Set rep_movsb_threshold to 2112 on processors with FSRM
Date: Fri, 30 Apr 2021 11:24:42 -0700 [thread overview]
Message-ID: <20210430182442.3612464-1-hjl.tools@gmail.com> (raw)
The glibc memcpy benchmark on Intel Core i7-1065G7 (Ice Lake) showed
that REP MOVSB became faster after 2112 bytes:
Vector + REP MOVSB REP MOVSB
length=2112, align1=0, align2=0: 24.20 24.40
length=2112, align1=1, align2=0: 26.07 23.13
length=2112, align1=0, align2=1: 27.18 28.13
length=2112, align1=1, align2=1: 26.23 25.16
length=2176, align1=0, align2=0: 23.18 22.52
length=2176, align1=2, align2=0: 25.45 22.52
length=2176, align1=0, align2=2: 27.14 27.82
length=2176, align1=2, align2=2: 22.73 25.56
length=2240, align1=0, align2=0: 24.62 24.25
length=2240, align1=3, align2=0: 29.77 27.15
length=2240, align1=0, align2=3: 35.55 29.93
length=2240, align1=3, align2=3: 34.49 25.15
length=2304, align1=0, align2=0: 34.75 26.64
length=2304, align1=4, align2=0: 32.09 22.63
length=2304, align1=0, align2=4: 28.43 31.24
Use REP MOVSB for data size > 2112 bytes in memcpy on processors with
fast short REP MOVSB (FSRM).
* sysdeps/x86/dl-cacheinfo.h (dl_init_cacheinfo): Set
rep_movsb_threshold to 2112 on processors with fast short REP
MOVSB (FSRM).
---
sysdeps/x86/dl-cacheinfo.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index d9944250fc..3f04fb5019 100644
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -871,7 +871,10 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
if (CPU_FEATURE_USABLE_P (cpu_features, AVX512F)
&& !CPU_FEATURE_PREFERRED_P (cpu_features, Prefer_No_AVX512))
{
- rep_movsb_threshold = 2048 * (64 / 16);
+ if (CPU_FEATURE_USABLE_P (cpu_features, FSRM))
+ rep_movsb_threshold = 2112;
+ else
+ rep_movsb_threshold = 2048 * (64 / 16);
#if HAVE_TUNABLES
minimum_rep_movsb_threshold = 64 * 8;
#endif
@@ -879,7 +882,10 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
else if (CPU_FEATURE_PREFERRED_P (cpu_features,
AVX_Fast_Unaligned_Load))
{
- rep_movsb_threshold = 2048 * (32 / 16);
+ if (CPU_FEATURE_USABLE_P (cpu_features, FSRM))
+ rep_movsb_threshold = 2112;
+ else
+ rep_movsb_threshold = 2048 * (32 / 16);
#if HAVE_TUNABLES
minimum_rep_movsb_threshold = 32 * 8;
#endif
--
2.31.1
next reply other threads:[~2021-04-30 18:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 18:24 H.J. Lu [this message]
2021-04-30 22:59 ` Noah Goldstein
2021-04-30 23:50 ` H.J. Lu
2021-05-01 0:17 ` Noah Goldstein
2021-05-01 1:26 ` H.J. Lu
2021-05-01 14:08 ` [PATCH v2] " H.J. Lu
2021-05-01 18:45 ` Noah Goldstein
2022-04-27 23:56 ` Sunil Pandey
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