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Date: Thu, 28 Jan 2016 11:05:04 -0600 (CST)
From: Christoph Lameter <cl@linux.com>
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To: Michal Hocko <mhocko@kernel.org>
cc: Mike Galbraith <umgwanakikbuti@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm, vmstat: make quiet_vmstat lighter (was: Re: fast
 path cycle muncher (vmstat: make vmstat_updater deferrable) again and shut
 down on idle)
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On Thu, 28 Jan 2016, Michal Hocko wrote:

> > You can drop the need_update check. refresh_cpu_vm_stats() does the same
> > checks in a more efficient way. If you keep this the checks will
> > performed twice.
>
> refresh_cpu_vm_stats does this_cpu_xchg for each counter. Is it really
> more effective than memchr_inv?

Ok makes sense.

Acked-by: Christoph Lameter <cl@linux.com>