linux-kernel - Re: [PATCH] locking/qspinlock: Use this_cpu_ptr instead of this_cpu

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Message-ID: <20160603113703.GK3190@twins.programming.kicks-ass.net>
Date:	Fri, 3 Jun 2016 13:37:03 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com, waiman.long@....com
Subject: Re: [PATCH] locking/qspinlock: Use this_cpu_ptr instead of
 this_cpu_dec

On Fri, Jun 03, 2016 at 05:48:50PM +0800, Pan Xinhui wrote:
> queued_spin_lock_slowpath should not worry about interrupt change
> node->count by accident because ->count is inc and dec when we
> enter/leave queued_spin_lock_slowpath.
> 
> So this_cpu_dec() does some no point things here, lets use this_cpu_ptr
> for a small optimization.

Uhm, have you actually looked at what that does on x86?