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Date: Thu, 07 Jun 2012 23:17:28 -0400
From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
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To: Anton Vorontsov <anton.vorontsov@linaro.org>
CC: Pekka Enberg <penberg@kernel.org>,
        Leonid Moiseichuk <leonid.moiseichuk@nokia.com>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
        Minchan Kim <minchan@kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        John Stultz <john.stultz@linaro.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org,
        patches@linaro.org, kernel-team@android.com
Subject: Re: [PATCH 1/5] vmstat: Implement refresh_vm_stats()
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(6/1/12 8:24 AM), Anton Vorontsov wrote:
> This function forcibly flushes per-cpu vmstat diff counters to the
> global counters.
> 
> Note that we don't try to flush percpu pagesets, the pcp will be
> still flushed once per 3 seconds.
> 
> Signed-off-by: Anton Vorontsov<anton.vorontsov@linaro.org>

No.

This is insane. Your patch improved vmevent accuracy a _bit_. But instead of,
decrease a performance of large systems. That's no good deal. 99% user never
uses vmevent.

MOREOVER, this patch don't solve vmevent accuracy issue AT ALL. because of,
a second is enough big to make large inaccuracy. Modern cpus are fast. Guys,
the fact is, user land monitor can't use implicit batch likes vmstat. That's
a reason why perf don't use vmstat. I suggest you see perf APIs. It may bring
you good inspiration.