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SubjectRe: [RFC 5/5] Memory controller soft limit reclaim on contention
> >>  #endif /* _LINUX_MEMCONTROL_H */
> >> diff -puN mm/vmscan.c~memory-controller-soft-limit-reclaim-on-contention mm/vmscan.c
> >> diff -puN mm/page_alloc.c~memory-controller-soft-limit-reclaim-on-contention mm/page_alloc.c
> >> --- linux-2.6.26-rc5/mm/page_alloc.c~memory-controller-soft-limit-reclaim-on-contention 2008-06-27 20:43:10.000000000 +0530
> >> +++ linux-2.6.26-rc5-balbir/mm/page_alloc.c 2008-06-27 20:43:10.000000000 +0530
> >> @@ -1669,7 +1669,14 @@ nofail_alloc:
> >> reclaim_state.reclaimed_slab = 0;
> >> p->reclaim_state = &reclaim_state;
> >>
> >> - did_some_progress = try_to_free_pages(zonelist, order, gfp_mask);
> >> + /*
> >> + * First try to reclaim from memory control groups that have
> >> + * exceeded their soft limit
> >> + */
> >> + did_some_progress = mem_cgroup_reclaim_on_contention(gfp_mask);
> >> + if (!did_some_progress)
> >> + did_some_progress = try_to_free_pages(zonelist, order,
> >> + gfp_mask);
> >
> > try_to_free_mem_cgroup_pages() assume memcg need only one page.
> > but this code break it.
> >
> > if anyone need several continuous memory, mem_cgroup_reclaim_on_contention() reclaim
> > one or a very few page and return >0, then cause page allocation failure.
> >
> > shouldn't we extend try_to_free_mem_cgroup_pages() agruments?
> >
> >
> > in addition, if we don't assume try_to_free_mem_cgroup_pages() need one page,
> > we should implement lumpy reclaim to mem_cgroup_isolate_pages().
> > otherwise, cpu wasting significant increase.
>
> The memory controller currently controls just *user* pages, which are all of
> order 1. Since pages are faulted in at different times, lumpy reclaim was not
> the highest priority for the memory controller. NOTE: the pages are duplicated
> on the per-zone LRU, so lumpy reclaim from there should work just fine.

yes, memcg used only one page.
but mem_cgroup_reclaim_on_contention() reclaim for generic alloc_pages(), instead for memcg.
we can't assume memcg usage.
isn't it?






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