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From 238aa7dce4d9684b6326665c79eabad72d5679bf Mon Sep 17 00:00:00 2001
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From: "H.J. Lu" <hjl.tools@gmail.com>
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Date: Wed, 2 Mar 2022 16:21:12 -0800
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Subject: [PATCH] x86: Set rep_movsb_threshold to 2112 on processors with FSRM
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The glibc memcpy benchmark on Intel Core i7-1065G7 (Ice Lake) showed
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that REP MOVSB became faster after 2112 bytes:
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Vector Move REP MOVSB
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length=2112, align1=0, align2=0: 24.20 24.40
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length=2112, align1=1, align2=0: 26.07 23.13
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length=2112, align1=0, align2=1: 27.18 28.13
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length=2112, align1=1, align2=1: 26.23 25.16
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length=2176, align1=0, align2=0: 23.18 22.52
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length=2176, align1=2, align2=0: 25.45 22.52
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length=2176, align1=0, align2=2: 27.14 27.82
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length=2176, align1=2, align2=2: 22.73 25.56
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length=2240, align1=0, align2=0: 24.62 24.25
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length=2240, align1=3, align2=0: 29.77 27.15
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length=2240, align1=0, align2=3: 35.55 29.93
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length=2240, align1=3, align2=3: 34.49 25.15
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length=2304, align1=0, align2=0: 34.75 26.64
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length=2304, align1=4, align2=0: 32.09 22.63
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length=2304, align1=0, align2=4: 28.43 31.24
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Use REP MOVSB for data size > 2112 bytes in memcpy on processors with
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fast short REP MOVSB (FSRM).
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* sysdeps/x86/dl-cacheinfo.h (dl_init_cacheinfo): Set
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rep_movsb_threshold to 2112 on processors with fast short REP
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MOVSB (FSRM).
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(cherry picked from commit cf2c57526ba4b57e6863ad4db8a868e2678adce8)
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---
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sysdeps/x86/cacheinfo.h | 6 ++++++
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1 file changed, 6 insertions(+)
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diff --git a/sysdeps/x86/cacheinfo.h b/sysdeps/x86/cacheinfo.h
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index f72f634a..cc3941d3 100644
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--- a/sysdeps/x86/cacheinfo.h
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+++ b/sysdeps/x86/cacheinfo.h
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@@ -430,6 +430,12 @@ init_cacheinfo (void)
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rep_movsb_threshold = 2048 * (16 / 16);
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minimum_rep_movsb_threshold = 16 * 8;
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}
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+
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+ /* NB: The default REP MOVSB threshold is 2112 on processors with fast
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+ short REP MOVSB (FSRM). */
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+ if (CPU_FEATURE_USABLE_P (cpu_features, FSRM))
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+ rep_movsb_threshold = 2112;
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+
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if (cpu_features->rep_movsb_threshold > minimum_rep_movsb_threshold)
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__x86_rep_movsb_threshold = cpu_features->rep_movsb_threshold;
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else
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--
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GitLab
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