linux-kernel - 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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Date:	Thu, 28 Jan 2016 11:05:04 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Michal Hocko <mhocko@...nel.org>
cc:	Mike Galbraith <umgwanakikbuti@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.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)

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@...ux.com>