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).

diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index d9944250fc87732333545eb8d333c1352f0e37b7..e6c94dfd023a25dcfcf5f90a98867957cd2f091c 100644 (file)
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -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