Messages in this thread | | | Subject | Re: [v3 PATCH 4/4] mm: thp: make deferred split shrinker memcg aware | From | Yang Shi <> | Date | Tue, 25 Jun 2019 15:33:40 -0700 |
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On 6/25/19 3:00 PM, Andrew Morton wrote: > On Thu, 13 Jun 2019 05:56:49 +0800 Yang Shi <yang.shi@linux.alibaba.com> wrote: > >> Currently THP deferred split shrinker is not memcg aware, this may cause >> premature OOM with some configuration. For example the below test would >> run into premature OOM easily: >> >> $ cgcreate -g memory:thp >> $ echo 4G > /sys/fs/cgroup/memory/thp/memory/limit_in_bytes >> $ cgexec -g memory:thp transhuge-stress 4000 >> >> transhuge-stress comes from kernel selftest. >> >> It is easy to hit OOM, but there are still a lot THP on the deferred >> split queue, memcg direct reclaim can't touch them since the deferred >> split shrinker is not memcg aware. >> >> Convert deferred split shrinker memcg aware by introducing per memcg >> deferred split queue. The THP should be on either per node or per memcg >> deferred split queue if it belongs to a memcg. When the page is >> immigrated to the other memcg, it will be immigrated to the target >> memcg's deferred split queue too. >> >> Reuse the second tail page's deferred_list for per memcg list since the >> same THP can't be on multiple deferred split queues. >> >> ... >> >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -4579,6 +4579,11 @@ static struct mem_cgroup *mem_cgroup_alloc(void) >> #ifdef CONFIG_CGROUP_WRITEBACK >> INIT_LIST_HEAD(&memcg->cgwb_list); >> #endif >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> + spin_lock_init(&memcg->deferred_split_queue.split_queue_lock); >> + INIT_LIST_HEAD(&memcg->deferred_split_queue.split_queue); >> + memcg->deferred_split_queue.split_queue_len = 0; >> +#endif >> idr_replace(&mem_cgroup_idr, memcg, memcg->id.id); >> return memcg; >> fail: >> @@ -4949,6 +4954,14 @@ static int mem_cgroup_move_account(struct page *page, >> __mod_memcg_state(to, NR_WRITEBACK, nr_pages); >> } >> >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> + if (compound && !list_empty(page_deferred_list(page))) { >> + spin_lock(&from->deferred_split_queue.split_queue_lock); >> + list_del(page_deferred_list(page)); > It's worrisome that this page still appears to be on the deferred_list > and that the above if() would still succeed. Should this be > list_del_init()?
list_del_init() sounds safe although I'm not quite sure this is possible. Will update this with fixing build issue together.
> >> + from->deferred_split_queue.split_queue_len--; >> + spin_unlock(&from->deferred_split_queue.split_queue_lock); >> + } >> +#endif
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