Re: [PATCH 3/4] powerpc/64: context switch an hwsync instruction can be avoided
From: Peter Zijlstra <peterz@infradead.org>
Date: 2017-06-08 20:12:33
On Fri, Jun 09, 2017 at 01:36:08AM +1000, Nicholas Piggin wrote:
The hwsync 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. Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>