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Date: Fri, 08 Jun 2012 02:57:47 -0400
From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
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To: Pekka Enberg <penberg@kernel.org>
CC: KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
        Anton Vorontsov <cbouatmailru@gmail.com>,
        Minchan Kim <minchan@kernel.org>,
        Leonid Moiseichuk <leonid.moiseichuk@nokia.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 0/5] Some vmevent fixes...
References: <20120507121527.GA19526@lizard> <4FA82056.2070706@gmail.com> <CAOJsxLHQcDZSHJZg+zbptqmT9YY0VTkPd+gG_zgMzs+HaV_cyA@mail.gmail.com> <CAHGf_=q1nbu=3cnfJ4qXwmngMPB-539kg-DFN2FJGig8+dRaNw@mail.gmail.com> <CAOJsxLFAavdDbiLnYRwe+QiuEHSD62+Sz6LJTk+c3J9gnLVQ_w@mail.gmail.com> <CAHGf_=pSLfAue6AR5gi5RQ7xvgTxpZckA=Ja1fO1AkoO1o_DeA@mail.gmail.com> <CAOJsxLG1+zhOKgi2Rg1eSoXSCU8QGvHVED_EefOOLP-6JbMDkg@mail.gmail.com> <20120601122118.GA6128@lizard> <alpine.LFD.2.02.1206032125320.1943@tux.localdomain> <4FCC7592.9030403@kernel.org> <20120604113811.GA4291@lizard> <4FCD14F1.1030105@gmail.com> <CAOJsxLGbX33TfGvMEzV4By=n8JojHcXV32FRueb3kmti38jBPQ@mail.gmail.com> <4FD177BD.1070004@gmail.com> <CAOJsxLGHDF_QnRSA_CckdTDGxNkOFvRNZoFoW0iGDjGvTCK=2A@mail.gmail.com>
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(6/8/12 2:54 AM), Pekka Enberg wrote:
> On Fri, Jun 8, 2012 at 6:55 AM, KOSAKI Motohiro
> <kosaki.motohiro@gmail.com>  wrote:
>>> For some cases, yes, but probably not for all.
>>>
>>> For example, if userspace doesn't know about "about to swap real soon"
>>> condition, it can continue to grow its caches making
>>> fallocate(VOLATILE) pretty much useless.
>>
>> Fair enough. But, Please consider your scenario don't need vmevent(2),
>> cat /proc/meminfo works enough. Only dropping activity need a quick work
>> and just in time notification. cache growing limitation don't need.
>
> Why do you keep bringing this up? Yes, you might get away with polling
> /proc/meminfo or /proc/vmstat for some specific cases. It does not
> make it a proper generic solution to the problem "vmevent" ABI tries
> to address.

Guys, current vmevent _is_ a polling interface. It only is wrapped kernel
timer.