Re: [PATCH] mm, memory_hotplug: do not back off draining pcp free pages from kworker context
From: Michal Hocko
Date: Tue Sep 19 2017 - 05:46:00 EST
On Mon 18-09-17 20:38:22, Tejun Heo wrote:
> Hello, Sorry about the delay.
> On Thu, Aug 31, 2017 at 07:33:42AM +0200, Michal Hocko wrote:
> > > > Michal, are you sure that this patch does not cause deadlock?
> > > >
> > > > As shown in "[PATCH] mm: Use WQ_HIGHPRI for mm_percpu_wq." thread, currently work
> > > > items on mm_percpu_wq seem to be blocked by other work items not on mm_percpu_wq.
> IIUC that wasn't a deadlock but more a legitimate starvation from too
> many tasks trying to reclaim directly.
> > > But we have a rescuer so we should make a forward progress eventually.
> > > Or am I missing something. Tejun, could you have a look please?
> > ping... I would really appreaciate if you could double check my thinking
> > Tejun. This is a tricky area and I would like to prevent further subtle
> > issues here.
> So, this shouldn't be an issue. This may get affected by direct
> reclaim frenzy but it's only a small piece of the whole symptom and we
> gotta fix that at the source.
OK, so there shouldn't be any issue with the patch, right?