Re: [PATCH v3 3/6] memcg: Simplify mem_cgroup_force_empty_list errorhandling

[Johannes Weiner]

On Wed, Nov 14, 2012 at 02:59:30PM +0100, Michal Hocko wrote:
> On Tue 13-11-12 16:10:41, Johannes Weiner wrote:
> > Would it make sense to stick a wait_on_page_locked() in there just so
> > that we don't busy spin on a page under migration/reclaim?
> 
> Hmm, this would also mean that get_page_unless_zero would fail as well
> and so we would schedule in mem_cgroup_force_empty_list. It is true that
> there might be no other runnable task so we can busy loop so yes this
> would help. Care to cook the patch?

Eventually get_page_unless_zero() would fail but we could still spin
on a page while it's off the LRU and migration performs writeback on
it e.g.  cond_resched() does not necessarily schedule just because
there is another runnable task, I think, it's voluntary preemption
when the task needs rescheduling anyway, not yield.

Maybe not worth bothering...
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