powerpc/64: Drop explicit hwsync in context switch
authorNicholas Piggin <npiggin@gmail.com>
Thu, 8 Jun 2017 15:36:08 +0000 (01:36 +1000)
committerMichael Ellerman <mpe@ellerman.id.au>
Thu, 15 Jun 2017 06:34:39 +0000 (16:34 +1000)
commit9145effd626d155484f73db24ab3e142ecda31db
tree0425c4849b69d9e4adc639a9e1969e95eb2d5901
parent837e72f78a72ef43a0c5e179f3addadb2a225f80
powerpc/64: Drop explicit hwsync in context switch

The sync (aka. hwsync, aka. heavyweight sync) in the context switch
code to prevent MMIO access being reordered from the point of view of
a single process if it gets migrated to a different CPU is not
required because there is an hwsync performed earlier in the context
switch path.

Comment this so it's clear enough if anything changes on the scheduler
or the powerpc sides. Remove the hwsync from _switch.

This improves context switch performance by 2-3% on POWER8.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
arch/powerpc/include/asm/barrier.h
arch/powerpc/kernel/entry_64.S