From: Michal Hocko <mhocko@kernel.org> To: roy.qing.li@gmail.com Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, hannes@cmpxchg.org, vdavydov@virtuozzo.com Subject: Re: [PATCH][V2] mm: memcontrol: fix the margin computation in mem_cgroup_margin Date: Wed, 25 May 2016 17:51:22 +0200 Message-ID: <20160525155122.GK20132@dhcp22.suse.cz> (raw) In-Reply-To: <1464068266-27736-1-git-send-email-roy.qing.li@gmail.com> On Tue 24-05-16 13:37:46, roy.qing.li@gmail.com wrote: > From: Li RongQing <roy.qing.li@gmail.com> > > The margin may be set to the difference value between memory limit and > memory count firstly. which maybe returned wrongly if memsw.count excess > memsw.limit, because try_charge forces charging __GFP_NOFAIL allocations, > which may result in memsw.limit excess. If we are below memory.limit > and there's nothing to reclaim to reduce memsw.usage, might end up > looping in try_charge forever. This is quite hard for me to grasp. What would you say about the following: " mem_cgroup_margin might return memory.limit - memory_count when the memsw.limit is in excess. This doesn't happen usually because we do not allow excess on hard limits and memory.limit <= memsw.limit but __GFP_NOFAIL charges can force the charge and cause the excess when no memory is really swapable (swap is full or no anonymous memory is left). " > > Signed-off-by: Li RongQing <roy.qing.li@gmail.com> > Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com> > Cc: Michal Hocko <mhocko@suse.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/memcontrol.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 00981d2..12aaadd 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1090,6 +1090,8 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg) > limit = READ_ONCE(memcg->memsw.limit); > if (count <= limit) > margin = min(margin, limit - count); > + else > + margin = 0; > } > > return margin; > -- > 2.1.4 -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply index Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-05-24 5:37 roy.qing.li 2016-05-25 15:51 ` Michal Hocko [this message] 2016-05-26 1:28 ` Li RongQing
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