Re: [PATCH 02/11] memcg: Reclaim when more than one page needed.

From: Glauber Costa
Date: Tue Jun 26 2012 - 04:42:36 EST


On 06/26/2012 03:33 AM, Suleiman Souhlal wrote:
On Mon, Jun 25, 2012 at 7:15 AM, Glauber Costa <glommer@xxxxxxxxxxxxx> wrote:
From: Suleiman Souhlal <ssouhlal@xxxxxxxxxxx>

mem_cgroup_do_charge() was written before slab accounting, and expects
three cases: being called for 1 page, being called for a stock of 32 pages,
or being called for a hugepage. If we call for 2 or 3 pages (and several
slabs used in process creation are such, at least with the debug options I
had), it assumed it's being called for stock and just retried without reclaiming.

Fix that by passing down a minsize argument in addition to the csize.

And what to do about that (csize == PAGE_SIZE && ret) retry? If it's
needed at all (and presumably is since it's there, perhaps to handle
races), then it should be extended to more than PAGE_SIZE, yet how far?
And should there be a retry count limit, of what? For now retry up to
COSTLY_ORDER (as page_alloc.c does), stay safe with a cond_resched(),
and make sure not to do it if __GFP_NORETRY.

The commit description mentions COSTLY_ORDER, but it's not actually
used in the patch.

-- Suleiman

Yeah, forgot to update the changelog =(

But much more importantly, are you still happy with those changes?

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