Re: [BUGFIX][PATCH 2/4] memcg: fix charge path for THP and allowearly retirement

From: Johannes Weiner
Date: Fri Jan 28 2011 - 02:57:33 EST

On Fri, Jan 28, 2011 at 12:26:08PM +0900, KAMEZAWA Hiroyuki wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> When THP is used, Hugepage size charge can happen. It's not handled
> correctly in mem_cgroup_do_charge(). For example, THP can fallback
> to small page allocation when HUGEPAGE allocation seems difficult
> or busy, but memory cgroup doesn't understand it and continue to
> try HUGEPAGE charging. And the worst thing is memory cgroup
> believes 'memory reclaim succeeded' if limit - usage > PAGE_SIZE.
> By this, khugepaged etc...can goes into inifinite reclaim loop
> if tasks in memcg are busy.
> After this patch
> - Hugepage allocation will fail if 1st trial of page reclaim fails.
> Changelog:
> - make changes small. removed renaming codes.
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)

Was there something wrong with my oneline fix?

Really, there is no way to make this a beautiful fix. The way this
function is split up makes no sense, and the constant addition of more
and more flags just to correctly communicate with _one callsite_
should be an obvious hint.
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