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

From: Rik van Riel
Date: Tue Jun 15 2010 - 10:38:32 EST

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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