linux-kernel - Re: Easy portable testcase! (Re: Kernel falls apart under light memory pressure (i.e. linking vmlinux))

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Date:	Tue, 14 Jun 2011 08:32:48 -0400
From:	Andrew Lutomirski <luto@....edu>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Minchan Kim <minchan.kim@...il.com>, mgorman@...e.de,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	aarcange@...hat.com, kamezawa.hiroyu@...fujitsu.com,
	fengguang.wu@...el.com, andi@...stfloor.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, riel@...hat.com
Subject: Re: Easy portable testcase! (Re: Kernel falls apart under light
 memory pressure (i.e. linking vmlinux))

On Tue, Jun 14, 2011 at 6:10 AM, Johannes Weiner <hannes@...xchg.org> wrote:
> On Sun, May 29, 2011 at 08:28:46PM -0400, Andrew Lutomirski wrote:
>> On Sun, May 29, 2011 at 2:28 PM, Minchan Kim <minchan.kim@...il.com> wrote:
>> >>
>> >> It works only if the zone meets high watermark. If allocation is
>> >> faster than reclaim(ie, it's true for slow swap device), the zone
>> >> would remain congested.
>> >> It means swapout would block.
>> >> As we see the OOM log, we can know that DMA32 zone can't meet high watermark.
>> >>
>> >> Does my guessing make sense?
>> >
>> > Hi Andrew.
>> > I got failed your scenario in my machine so could you be willing to
>> > test this patch for proving my above scenario?
>> > The patch is just revert patch of 0e093d99[do not sleep on the
>> > congestion queue...] for 2.6.38.6.
>> > I would like to test it for proving my above zone congestion scenario.
>> >
>> > I did it based on 2.6.38.6 for your easy apply so you must apply it
>> > cleanly on vanilla v2.6.38.6.
>> > And you have to add !pgdat_balanced and shrink_slab patch.
>>
>> No, because my laptop just decided that it doesn't like to turn on. :(
>>
>> I'll test it on my VM on Tuesday and (fingers crossed) on my repaired
>> laptop next weekend.
>
> Any updates on this?
>

Sorry, got distracted by writing my thesis.

This patch (Revert "writeback: do not sleep on the congestion queue if
there are no congested BDIs or if significant congestion is not being
encountered in the current zone") does not fix the problem; if
anything it triggers more easily with the patch (at least in KVM).

--Andy
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