Re: [PATCH 12/12] vmscan: Do not writeback pages in direct reclaim

[Rik van Riel]

On 06/15/2010 09:37 AM, Christoph Hellwig wrote:
> On Tue, Jun 15, 2010 at 09:34:18AM -0400, Rik van Riel wrote:
> > If direct reclaim can overflow the stack, so can direct
> > memcg reclaim.  That means this patch does not solve the
> > stack overflow, while admitting that we do need the
> > ability to get specific pages flushed to disk from the
> > pageout code.
>
> Can you explain what the hell memcg reclaim is and why it needs
> to reclaim from random contexts?

The page fault code will call the cgroup accounting code.

When a cgroup goes over its memory limit, __mem_cgroup_try_charge
will call mem_cgroup_hierarchical_reclaim, which will then go
into the page reclaim code.

> It seems everything that has a cg in it's name that I stumbled over
> lately seems to be some ugly wart..

No argument there.  It took me a few minutes to find the code
path above :)

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