powerpc: Tweak copy selection parameter in __copy_tofrom_user_power7()
authorAndrew Jeffery <andrew@aj.id.au>
Fri, 12 May 2017 03:58:10 +0000 (13:28 +0930)
committerMichael Ellerman <mpe@ellerman.id.au>
Tue, 30 May 2017 04:59:51 +0000 (14:59 +1000)
commita3f952df3c6d205fe3b1e0e4848d3c3db4a28ef0
tree4b5fe78d44151ba3f2c7ee22ca7c588867d0b3c7
parent09b6c1129f899c72d70b8bea36020644aa3b5a28
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: Andrew Jeffery <andrew@aj.id.au>
Acked-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
arch/powerpc/lib/copyuser_power7.S