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Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace

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On Tue 10-05-16 16:07:14, Joonsoo Kim wrote:
> 2016-05-05 4:40 GMT+09:00 Michal Hocko <mhocko@kernel.org>:
> > On Thu 05-05-16 00:30:35, Joonsoo Kim wrote:
> >> 2016-05-04 18:21 GMT+09:00 Michal Hocko <mhocko@kernel.org>:
> > [...]
> >> > Do we really consume 512B of stack during reclaim. That sounds more than
> >> > worrying to me.
> >>
> >> Hmm...I checked it by ./script/stackusage and result is as below.
> >>
> >> shrink_zone() 128
> >> shrink_zone_memcg() 248
> >> shrink_active_list() 176
> >>
> >> We have a call path that shrink_zone() -> shrink_zone_memcg() ->
> >> shrink_active_list().
> >> I'm not sure whether it is the deepest path or not.
> >
> > This is definitely not the deepest path. Slab shrinkers can take more
> > but 512B is still a lot. Some call paths are already too deep when
> > calling into the allocator and some of them already use GFP_NOFS to
> > prevent from potentially deep callchain slab shrinkers. Anyway worth
> > exploring for better solutions.
> >
> > And I believe it would be better to solve this in the stackdepot
> > directly so other users do not have to invent their own ways around the
> > same issue. I have just checked the code and set_track uses save_stack
> > which does the same thing and it seems to be called from the slab
> > allocator. I have missed this usage before so the problem already does
> > exist. It would be unfair to request you to fix that in order to add a
> > new user. It would be great if this got addressed though.
> 
> Yes, fixing it in stackdepot looks more reasonable.
> Then, I will just change PAGE_OWNER_STACK_DEPTH from 64 to 16 and
> leave the code as is for now. With this change, we will just consume 128B stack
> and would not cause stack problem. If anyone has an objection,
> please let me know.

128B is still quite a lot but considering there is a plan to make it
more robust I can live with it as a temporary workaround.

-- 
Michal Hocko
SUSE Labs

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[PATCH 0/6] mm/page_owner: use tackdepot to store stacktrace js1304@gmail.com - 2016-05-03 07:30 +0200
  [PATCH 5/6] tools/vm/page_owner: increase temporary buffer size js1304@gmail.com - 2016-05-03 07:30 +0200
  [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-03 11:00 +0200
      Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-04 04:20 +0200
        Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-04 04:40 +0200
          Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-04 11:30 +0200
            Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <js1304@gmail.com> - 2016-05-04 17:40 +0200
        Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-04 11:30 +0200
          Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <js1304@gmail.com> - 2016-05-04 17:40 +0200
            Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <js1304@gmail.com> - 2016-05-04 17:50 +0200
              Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-04 21:50 +0200
            Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-04 21:50 +0200
              Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <js1304@gmail.com> - 2016-05-10 09:10 +0200
                Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-10 11:00 +0200
    Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Vlastimil Babka <vbabka@suse.cz> - 2016-05-12 14:00 +0200
  [PATCH 3/6] mm/page_owner: copy last_migrate_reason in copy_page_owner() js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 3/6] mm/page_owner: copy last_migrate_reason in  copy_page_owner() Vlastimil Babka <vbabka@suse.cz> - 2016-05-10 17:20 +0200
      Re: [PATCH 3/6] mm/page_owner: copy last_migrate_reason in  copy_page_owner() Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-12 05:00 +0200
        Re: [PATCH 3/6] mm/page_owner: copy last_migrate_reason in  copy_page_owner() Vlastimil Babka <vbabka@suse.cz> - 2016-05-12 08:50 +0200
  [PATCH 4/6] mm/page_owner: introduce split_page_owner and replace manual handling js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 4/6] mm/page_owner: introduce split_page_owner and replace  manual handling Vlastimil Babka <vbabka@suse.cz> - 2016-05-10 17:20 +0200
  [PATCH 2/6] mm/page_owner: initialize page owner without holding the zone lock js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 2/6] mm/page_owner: initialize page owner without holding  the zone lock Vlastimil Babka <vbabka@suse.cz> - 2016-05-10 17:10 +0200
  [PATCH 1/6] mm/compaction: split freepages without holding the zone lock js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 1/6] mm/compaction: split freepages without holding the  zone lock Vlastimil Babka <vbabka@suse.cz> - 2016-05-10 17:00 +0200
      Re: [PATCH 1/6] mm/compaction: split freepages without holding the  zone lock Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-12 05:00 +0200

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