powerpc/64: Drop explicit hwsync in context switch

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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>

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Nicholas Piggin 2017-06-09 01:36:08 +10:00 • committed by Michael Ellerman

parent 837e72f78a

commit 9145effd62

2 changed files with 22 additions and 6 deletions

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5

arch/powerpc/include/asm/barrier.h

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23

arch/powerpc/kernel/entry_64.S

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