Re: readahead and oom

[Dave Young]

On Tue, Apr 26, 2011 at 2:25 PM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> On Tue, Apr 26, 2011 at 02:07:17PM +0800, Dave Young wrote:
>> On Tue, Apr 26, 2011 at 2:05 PM, Dave Young <hidave.darkstar@xxxxxxxxx> wrote:
>> > On Tue, Apr 26, 2011 at 1:55 PM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
>> >> On Tue, Apr 26, 2011 at 01:49:25PM +0800, Dave Young wrote:
>> >>> Hi,
>> >>>
>> >>> When memory pressure is high, readahead could cause oom killing.
>> >>> IMHO we should stop readaheading under such circumstancesãIf it's true
>> >>> how to fix it?
>> >>
>> >> Good question. Before OOM there will be readahead thrashings, which
>> >> can be addressed by this patch:
>> >>
>> >> http://lkml.org/lkml/2010/2/2/229
>> >
>> > Hi, I'm not clear about the patch, could be regard as below cases?
>> > 1) readahead alloc fail due to low memory such as other large allocation
>>
>> For example vm balloon allocate lots of memory, then readahead could
>> fail immediately and then oom
>
> If true, that would be the problem of vm balloon. It's not good to
> consume lots of memory all of a sudden, which will likely impact lots
> of kernel subsystems.
>
> btw readahead page allocations are completely optional. They are OK to
> fail and in theory shall not trigger OOM on themselves. We may
> consider passing __GFP_NORETRY for readahead page allocations.

Good idea, care to submit a patch?

-- 
Regards
dave
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