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Date: Thu, 28 Jan 2016 10:40:10 -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)
In-Reply-To: <20160128152119.GB15948@dhcp22.suse.cz>
Message-ID: <alpine.DEB.2.20.1601281039070.5481@east.gentwo.org>
References: <alpine.DEB.2.20.1601210941540.7063@east.gentwo.org> <20160121165148.GF29520@dhcp22.suse.cz> <alpine.DEB.2.20.1601211130580.7741@east.gentwo.org> <20160122140418.GB19465@dhcp22.suse.cz> <alpine.DEB.2.20.1601220950290.17929@east.gentwo.org>
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 <20160128152119.GB15948@dhcp22.suse.cz>
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On Thu, 28 Jan 2016, Michal Hocko wrote:

> +void quiet_vmstat(void)
> +{
> +	if (system_state != SYSTEM_RUNNING)
> +		return;
> +
> +	/*
> +	 * If we are already in hands of the shepherd then there
> +	 * is nothing for us to do here.
> +	 */
> +	if (cpumask_test_and_set_cpu(smp_processor_id(), cpu_stat_off))
> +		return;
> +
> +	if (!need_update(smp_processor_id()))
> +		return;
> +

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.

> +	/*
> +	 * Just refresh counters and do not care about the pending delayed
> +	 * vmstat_update. It doesn't fire that often to matter and canceling
> +	 * it would be too expensive from this path.
> +	 * vmstat_shepherd will take care about that for us.
> +	 */
> +	refresh_cpu_vm_stats(false);
> +}
> +
>