Commit a3f952df authored by Andrew Jeffery's avatar Andrew Jeffery Committed by Michael Ellerman

powerpc: Tweak copy selection parameter in __copy_tofrom_user_power7()

Experiments with the netperf benchmark indicated that the size selecting
VMX-based copies in __copy_tofrom_user_power7() was suboptimal on POWER8.
Measurements showed that parity was in the neighbourhood of 3328 bytes,
rather than greater than 4096. The change gives a 1.5-2.0% improvement in
performance for 4096-byte buffers, reducing the relative time spent in
__copy_tofrom_user_power7() from approximately 7% to approximately 5% in
the TCP_RR benchmark.
Signed-off-by: default avatarAndrew Jeffery <andrew@aj.id.au>
Acked-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 09b6c112
......@@ -82,14 +82,14 @@
_GLOBAL(__copy_tofrom_user_power7)
#ifdef CONFIG_ALTIVEC
cmpldi r5,16
cmpldi cr1,r5,4096
cmpldi cr1,r5,3328
std r3,-STACKFRAMESIZE+STK_REG(R31)(r1)
std r4,-STACKFRAMESIZE+STK_REG(R30)(r1)
std r5,-STACKFRAMESIZE+STK_REG(R29)(r1)
blt .Lshort_copy
bgt cr1,.Lvmx_copy
bge cr1,.Lvmx_copy
#else
cmpldi r5,16
......
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