Re: [PATCH] update sc->nr_reclaimed after each shrink_slab

[Vladimir Davydov]

On Fri, Jul 22, 2016 at 09:49:13AM +0200, Michal Hocko wrote:
> On Fri 22-07-16 11:43:30, Zhou Chengming wrote:
> > In !global_reclaim(sc) case, we should update sc->nr_reclaimed after each
> > shrink_slab in the loop. Because we need the correct sc->nr_reclaimed
> > value to see if we can break out.
> 
> Does this actually change anything? Maybe I am missing something but
> try_to_free_mem_cgroup_pages which is the main entry for the memcg
> reclaim doesn't set reclaim_state. I don't remember why... Vladimir?

We don't set reclaim_state on memcg reclaim, because there might be a
lot of unrelated slab objects freed from the interrupt context (e.g.
RCU freed) while we're doing memcg reclaim. Obviously, we don't want
them to contribute to nr_reclaimed.

Link to the thread with the problem discussion:

  http://marc.info/?l=linux-kernel&m=142132698209680&w=2