From: Rik van Riel <riel@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Satoru Moriya <satoru.moriya@hds.com>,
David Rientjes <rientjes@google.com>,
Randy Dunlap <rdunlap@xenotime.net>,
Satoru Moriya <smoriya@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"lwoodman@redhat.com" <lwoodman@redhat.com>,
Seiji Aguchi <saguchi@redhat.com>,
"hughd@google.com" <hughd@google.com>,
"hannes@cmpxchg.org" <hannes@cmpxchg.org>
Subject: Re: [PATCH -v2 -mm] add extra free kbytes tunable
Date: Wed, 12 Oct 2011 09:09:17 -0400 [thread overview]
Message-ID: <4E95917D.3080507@redhat.com> (raw)
In-Reply-To: <20111011135445.f580749b.akpm@linux-foundation.org>
On 10/11/2011 04:54 PM, Andrew Morton wrote:
> On Tue, 11 Oct 2011 16:23:22 -0400
> Satoru Moriya<satoru.moriya@hds.com> wrote:
>
>> On 10/11/2011 03:55 PM, Andrew Morton wrote:
>>> On Tue, 11 Oct 2011 15:32:11 -0400
>>> Satoru Moriya<satoru.moriya@hds.com> wrote:
>>>
>>>> On 10/10/2011 06:37 PM, Andrew Morton wrote:
>>>>> On Fri, 7 Oct 2011 20:08:19 -0700 (PDT) David Rientjes
>>>>> <rientjes@google.com> wrote:
>>>>>
>>>>>> On Thu, 1 Sep 2011, Rik van Riel wrote:
>>>>
>>>> Actually page allocator decreases min watermark to 3/4 * min
>>>> watermark for rt-task. But in our case some applications create a lot
>>>> of processes and if all of them are rt-task, the amount of watermark
>>>> bonus(1/4 * min watermark) is not enough.
>>>>
>>>> If we can tune the amount of bonus, it may be fine. But that is
>>>> almost all same as extra free kbytes.
>>>
>>> This situation is detectable at runtime. If realtime tasks are being
>>> stalled in the page allocator then start to increase the free-page
>>> reserves. A little control system.
>>
>> Detecting at runtime is too late for some latency critical systems.
>> At that system, we must avoid a stall before it happens.
>
> It's pretty darn obvious that the kernel can easily see the situation
> developing before it happens. By comparing a few integers.
The problem is that we may be dealing with bursts, not steady
states of allocations. Without knowing the size of a burst,
we have no idea when we should wake up kswapd to get enough
memory freed ahead of the application's allocations.
> Look, please don't go bending over backwards like this to defend a bad
> patch. It's a bad patch! It would be better not to have to merge it.
> Let's do something better.
I would love it if we could come up with something better,
and have thought about it a lot.
However, so far we do not seem to have an alternative yet :(
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next prev parent reply other threads:[~2011-10-12 13:09 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-01 14:52 [PATCH -mm] add extra free kbytes tunable Rik van Riel
2011-09-01 17:06 ` Randy Dunlap
2011-09-01 19:26 ` [PATCH -v2 " Rik van Riel
2011-09-01 21:58 ` Andrew Morton
2011-09-01 22:08 ` David Rientjes
2011-09-01 22:16 ` Andrew Morton
2011-09-02 16:31 ` Satoru Moriya
2011-10-13 7:33 ` Minchan Kim
2011-10-13 8:09 ` KAMEZAWA Hiroyuki
[not found] ` <E1FA588BC672D846BDBB452FCA1E308C2389B4@USINDEVS02.corp.hds.com>
2011-09-15 3:33 ` Satoru Moriya
2011-09-01 22:09 ` Andrew Morton
2011-09-02 16:26 ` [PATCH -mm] fixes & cleanups for "add extra free kbytes tunable" Rik van Riel
2011-09-30 21:43 ` [PATCH -v2 -mm] add extra free kbytes tunable Johannes Weiner
2011-10-08 3:08 ` David Rientjes
2011-10-10 22:37 ` Andrew Morton
2011-10-11 19:32 ` Satoru Moriya
2011-10-11 19:54 ` Andrew Morton
2011-10-11 20:23 ` Satoru Moriya
2011-10-11 20:54 ` Andrew Morton
2011-10-12 13:09 ` Rik van Riel [this message]
2011-10-12 19:20 ` Andrew Morton
2011-10-12 19:58 ` Rik van Riel
2011-10-12 20:26 ` David Rientjes
2011-10-21 23:48 ` Satoru Moriya
2011-10-23 21:22 ` David Rientjes
2011-10-25 2:04 ` Satoru Moriya
2011-10-25 21:50 ` David Rientjes
2011-10-26 18:59 ` Satoru Moriya
2011-10-12 21:08 ` Satoru Moriya
2011-10-12 22:41 ` David Rientjes
2011-10-12 23:52 ` Satoru Moriya
2011-10-13 0:01 ` David Rientjes
2011-10-13 5:35 ` KAMEZAWA Hiroyuki
2011-10-13 20:55 ` David Rientjes
2011-10-14 22:16 ` Satoru Moriya
2011-10-14 22:46 ` David Rientjes
2011-10-14 5:32 ` Satoru Moriya
2011-10-14 5:06 ` Satoru Moriya
2011-10-11 23:22 ` David Rientjes
2011-10-13 16:54 ` Satoru Moriya
2011-10-13 20:48 ` David Rientjes
2011-10-13 21:11 ` Rik van Riel
2011-10-13 22:02 ` David Rientjes
2011-10-11 19:20 ` Satoru Moriya
2011-10-11 21:04 ` David Rientjes
2011-10-12 13:13 ` Rik van Riel
2011-10-12 20:21 ` David Rientjes
2011-10-13 4:13 ` Rik van Riel
2011-10-13 5:22 ` David Rientjes
2011-10-22 0:11 ` Satoru Moriya
-- strict thread matches above, loose matches on Subject: below --
2011-09-09 23:01 Satoru Moriya
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