From: <leonid.moiseichuk@nokia.com>
To: <anton.vorontsov@linaro.org>, <kosaki.motohiro@gmail.com>,
        <penberg@kernel.org>
CC: <b.zolnierkie@samsung.com>, <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 2/5] vmevent: Convert from deferred timer to deferred
 work
Thread-Topic: [PATCH 2/5] vmevent: Convert from deferred timer to deferred
 work
Thread-Index: AQHNP/HM8KMmZkc4xkKq2ZDXaeCP2Zbvq0sAgAA7gACAACLOoA==
Date: Fri, 8 Jun 2012 07:05:46 +0000
Message-ID: <84FF21A720B0874AA94B46D76DB98269045F7890@008-AM1MPN1-004.mgdnok.nokia.com>
References: <20120601122118.GA6128@lizard>
 <1338553446-22292-2-git-send-email-anton.vorontsov@linaro.org>
 <4FD170AA.10705@gmail.com> <20120608065828.GA1515@lizard>
In-Reply-To: <20120608065828.GA1515@lizard>
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> -----Original Message-----
> From: ext Anton Vorontsov [mailto:anton.vorontsov@linaro.org]
> Sent: 08 June, 2012 09:58
...
> If you're saying that we should set up a timer in the userland and constantly
> read /proc/vmstat, then we will cause CPU wake up every 100ms, which is
> not acceptable. Well, we can try to introduce deferrable timers for the
> userspace. But then it would still add a lot more overhead for our task, as this
> solution adds other two context switches to read and parse /proc/vmstat. I
> guess this is not a show-stopper though, so we can discuss this.
> 
> Leonid, Pekka, what do you think about the idea?

Seems to me not nice solution. Generating/parsing vmstat every 100ms plus wakeups it is what exactly should be avoid to have sense to API.
It also will cause page trashing because user-space code could be pushed out from cache if VM decide. 

> 
> Thanks,
> 
> --
> Anton Vorontsov
> Email: cbouatmailru@gmail.com
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