From: Johannes Weiner <hannes@cmpxchg.org>
To: Michal Hocko <mhocko@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>, Tejun Heo <tj@kernel.org>,
Vladimir Davydov <vdavydov@parallels.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [patch 13/13] mm: memcontrol: rewrite uncharge API
Date: Tue, 15 Jul 2014 11:46:43 -0400 [thread overview]
Message-ID: <20140715154643.GT29639@cmpxchg.org> (raw)
In-Reply-To: <20140715151818.GE9366@dhcp22.suse.cz>
On Tue, Jul 15, 2014 at 05:18:18PM +0200, Michal Hocko wrote:
> On Tue 15-07-14 11:09:37, Johannes Weiner wrote:
> > On Tue, Jul 15, 2014 at 04:23:50PM +0200, Michal Hocko wrote:
> > > On Tue 15-07-14 10:25:45, Michal Hocko wrote:
> [...]
> > > > @@ -2760,15 +2752,15 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
> > > > spin_unlock_irq(&zone->lru_lock);
> > > > }
> > > >
> > > > - mem_cgroup_charge_statistics(memcg, page, anon, nr_pages);
> > > > - unlock_page_cgroup(pc);
> > > > -
> > > > + local_irq_disable();
> > > > + mem_cgroup_charge_statistics(memcg, page, nr_pages);
> > > > /*
> > > > * "charge_statistics" updated event counter. Then, check it.
> > > > * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
> > > > * if they exceeds softlimit.
> > > > */
> > > > memcg_check_events(memcg, page);
> > > > + local_irq_enable();
> > >
> > > preempt_{enable,disbale} should be sufficient for
> > > mem_cgroup_charge_statistics and memcg_check_events no?
> > > The first one is about per-cpu accounting (and that should be atomic
> > > wrt. IRQ on the same CPU) and the later one uses IRQ safe locks down in
> > > mem_cgroup_update_tree.
> >
> > How could it be atomic wrt. IRQ on the local CPU when IRQs that modify
> > the counters can fire on the local CPU?
>
> I meant that __this_atomic_add and __this_cpu_inc should be atomic wrt. IRQ.
> We do not care that an IRQ might jump in between two per-cpu operations.
> This is racy from other CPUs anyway.
It's really about a single RMW (+=) being interrupted by an IRQ.
this_cpu_ guarantees IRQ-atomicity, but __this_cpu_ does not.
We could probably migrate this code over to this_cpu and get rid of
the IRQ disabling later, because, as you said, we don't care about
being interrupted between separate counter updates.
next prev parent reply other threads:[~2014-07-15 15:46 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-18 20:40 [patch 00/13] mm: memcontrol: naturalize charge lifetime v4 Johannes Weiner
2014-06-18 20:40 ` [patch 01/13] mm: memcontrol: fold mem_cgroup_do_charge() Johannes Weiner
2014-06-18 20:40 ` [patch 02/13] mm: memcontrol: rearrange charging fast path Johannes Weiner
2014-06-18 20:40 ` [patch 03/13] mm: memcontrol: reclaim at least once for __GFP_NORETRY Johannes Weiner
2014-06-18 20:40 ` [patch 04/13] mm: huge_memory: use GFP_TRANSHUGE when charging huge pages Johannes Weiner
2014-06-18 20:40 ` [patch 05/13] mm: memcontrol: retry reclaim for oom-disabled and __GFP_NOFAIL charges Johannes Weiner
2014-06-18 20:40 ` [patch 06/13] mm: memcontrol: remove explicit OOM parameter in charge path Johannes Weiner
2014-06-18 20:40 ` [patch 07/13] mm: memcontrol: simplify move precharge function Johannes Weiner
2014-06-18 20:40 ` [patch 08/13] mm: memcontrol: catch root bypass in move precharge Johannes Weiner
2014-06-18 20:40 ` [patch 09/13] mm: memcontrol: use root_mem_cgroup res_counter Johannes Weiner
2014-06-18 20:40 ` [patch 10/13] mm: memcontrol: remove ordering between pc->mem_cgroup and PageCgroupUsed Johannes Weiner
2014-06-18 20:40 ` [patch 11/13] mm: memcontrol: do not acquire page_cgroup lock for kmem pages Johannes Weiner
2014-06-18 20:40 ` [patch 12/13] mm: memcontrol: rewrite charge API Johannes Weiner
2014-06-23 6:15 ` Uwe Kleine-König
2014-06-23 9:30 ` Michal Hocko
2014-06-23 9:42 ` Uwe Kleine-König
2014-07-14 15:04 ` Michal Hocko
2014-07-14 17:13 ` Johannes Weiner
2014-07-14 18:43 ` Michal Hocko
2014-06-18 20:40 ` [patch 13/13] mm: memcontrol: rewrite uncharge API Johannes Weiner
2014-06-20 16:36 ` [PATCH -mm] memcg: mem_cgroup_charge_statistics needs preempt_disable Michal Hocko
2014-06-23 4:16 ` Johannes Weiner
2014-06-21 0:34 ` [patch 13/13] mm: memcontrol: rewrite uncharge API Sasha Levin
2014-06-21 0:56 ` Andrew Morton
2014-06-21 1:03 ` Sasha Levin
2014-07-15 8:25 ` Michal Hocko
2014-07-15 12:19 ` Michal Hocko
2014-07-18 7:12 ` Michal Hocko
2014-07-18 14:45 ` Johannes Weiner
2014-07-18 15:12 ` Miklos Szeredi
2014-07-19 17:39 ` Johannes Weiner
2014-07-22 15:08 ` Michal Hocko
2014-07-22 15:44 ` Miklos Szeredi
2014-07-23 14:38 ` Michal Hocko
2014-07-23 15:06 ` Johannes Weiner
2014-07-23 15:19 ` Michal Hocko
2014-07-23 15:36 ` Johannes Weiner
2014-07-23 18:08 ` Miklos Szeredi
2014-07-23 21:02 ` Johannes Weiner
2014-07-24 8:46 ` Michal Hocko
2014-07-24 9:02 ` Michal Hocko
2014-07-25 15:26 ` Johannes Weiner
2014-07-25 15:43 ` Michal Hocko
2014-07-25 17:34 ` Johannes Weiner
2014-07-15 14:23 ` Michal Hocko
2014-07-15 15:09 ` Johannes Weiner
2014-07-15 15:18 ` Michal Hocko
2014-07-15 15:46 ` Johannes Weiner [this message]
2014-07-15 15:56 ` Michal Hocko
2014-07-15 15:55 ` Naoya Horiguchi
2014-07-15 16:07 ` Michal Hocko
2014-07-15 17:34 ` Johannes Weiner
2014-07-15 18:21 ` Michal Hocko
2014-07-15 18:43 ` Naoya Horiguchi
2014-07-15 19:04 ` Johannes Weiner
2014-07-15 20:49 ` Naoya Horiguchi
2014-07-15 21:48 ` Johannes Weiner
2014-07-16 7:55 ` Michal Hocko
2014-07-16 13:30 ` Naoya Horiguchi
2014-07-16 14:14 ` Johannes Weiner
2014-07-16 14:57 ` Naoya Horiguchi
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