On Thu, Jul 12, 2012 at 04:54:07PM +0800, Wanpeng Li wrote:

On Wed, Jul 11, 2012 at 07:02:13PM +0200, Johannes Weiner wrote:

quoted

Compaction (and page migration in general) can currently be hindered
through pages being owned by memory cgroups that are at their limits
and unreclaimable.

The reason is that the replacement page is being charged against the
limit while the page being replaced is also still charged.  But this
seems unnecessary, given that only one of the two pages will still be
in use after migration finishes.

This patch changes the memcg migration sequence so that the
replacement page is not charged.  Whatever page is still in use after
successful or failed migration gets to keep the charge of the page
that was going to be replaced.

The replacement page will still show up temporarily in the rss/cache
statistics, this can be fixed in a later patch as it's less urgent.

So I want to know after this patch be merged if mem_cgroup_wait_acct_move
still make sense, if the answer is no, I will send a patch to remove it.

This change is about migrating a charge from one physical page to
another, account moving is about migrating charges between groups.

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