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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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