From: Peter Zijlstra <peterz@infradead.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 3/4] powerpc/64: context switch an hwsync instruction can be avoided
Date: Thu, 8 Jun 2017 22:12:26 +0200 [thread overview]
Message-ID: <20170608201226.GD8337@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20170608153609.19217-3-npiggin@gmail.com>
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>
next prev parent reply other threads:[~2017-06-08 20:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-08 15:36 [PATCH 1/4] powerpc/64s: context switch leave interrupts hard enabled for radix Nicholas Piggin
2017-06-08 15:36 ` [PATCH 2/4] powerpc/64: context switch avoid reservation-clearing instruction Nicholas Piggin
2017-06-14 13:07 ` Michael Ellerman
2017-06-08 15:36 ` [PATCH 3/4] powerpc/64: context switch an hwsync instruction can be avoided Nicholas Piggin
2017-06-08 20:12 ` Peter Zijlstra [this message]
2017-06-08 15:36 ` [PATCH 4/4] powerpc/64s: context switch avoid cpabort Nicholas Piggin
2017-06-19 12:25 ` [1/4] powerpc/64s: context switch leave interrupts hard enabled for radix Michael Ellerman
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