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x86: Set rep_movsb_threshold to 2112 on processors with FSRM 

The glibc memcpy benchmark on Intel Core i7-1065G7 (Ice Lake) showed
that REP MOVSB became faster after 2112 bytes:

                                      Vector Move       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).
This commit is contained in:
H.J. Lu 2021-04-30 05:58:59 -07:00
parent 98544f5bcf
commit cf2c57526b
1 changed files with 4 additions and 0 deletions
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sysdeps/x86/dl-cacheinfo.h
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@ -891,6 +891,10 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
minimum_rep_movsb_threshold = 16 * 8;
#endif
}
/* NB: The default REP MOVSB threshold is 2112 on processors with fast
short REP MOVSB (FSRM). */
if (CPU_FEATURE_USABLE_P (cpu_features, FSRM))
rep_movsb_threshold = 2112;
unsigned long int rep_movsb_stop_threshold;
/* ERMS feature is implemented from AMD Zen3 architecture and it is