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    SubjectRe: [RFC 5/5] Memory controller soft limit reclaim on contention
    Hi

    this code survive stress testing?


    > + while (count-- &&
    > + ((mem = heap_delete_max(&mem_cgroup_heap)) != NULL)) {
    > + BUG_ON(!mem->on_heap);
    > + spin_unlock_irqrestore(&mem_cgroup_heap_lock, flags);
    > + nr_reclaimed += try_to_free_mem_cgroup_pages(mem,
    > + gfp_mask);
    > + cond_resched();
    > + spin_lock_irqsave(&mem_cgroup_heap_lock, flags);
    > + mem->on_heap = 0;
    > + /*
    > + * What should be the basis of breaking out?
    > + */
    > + if (nr_reclaimed)
    > + goto done;

    doubtful shortcut.
    we shouldn't assume we need only one page.



    > #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.






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