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 [thread overview] 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>
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> To: roy.qing.li-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org Subject: Re: [PATCH][V2] mm: memcontrol: fix the margin computation in mem_cgroup_margin Date: Wed, 25 May 2016 17:51:22 +0200 [thread overview] Message-ID: <20160525155122.GK20132@dhcp22.suse.cz> (raw) In-Reply-To: <1464068266-27736-1-git-send-email-roy.qing.li-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> On Tue 24-05-16 13:37:46, roy.qing.li-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote: > From: Li RongQing <roy.qing.li-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> > > 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-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> > Acked-by: Vladimir Davydov <vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org> > Cc: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org> Acked-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org> > --- > 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
next prev parent reply other threads:[~2016-05-25 15:51 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-05-24 5:37 [PATCH][V2] mm: memcontrol: fix the margin computation in mem_cgroup_margin roy.qing.li 2016-05-24 5:37 ` roy.qing.li-Re5JQEeQqe8AvxtiuMwx3w 2016-05-25 15:51 ` Michal Hocko [this message] 2016-05-25 15:51 ` Michal Hocko 2016-05-26 1:28 ` Li RongQing
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20160525155122.GK20132@dhcp22.suse.cz \ --to=mhocko@kernel.org \ --cc=cgroups@vger.kernel.org \ --cc=hannes@cmpxchg.org \ --cc=linux-mm@kvack.org \ --cc=roy.qing.li@gmail.com \ --cc=vdavydov@virtuozzo.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.