From: Michal Hocko <mhocko@suse.cz>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [RFC 4/5] memcg: make sure that memcg is not offline when charging
Date: Mon, 3 Feb 2014 17:44:55 +0100 [thread overview]
Message-ID: <20140203164455.GL2495@dhcp22.suse.cz> (raw)
In-Reply-To: <20140203161823.GJ6963@cmpxchg.org>
On Mon 03-02-14 11:18:23, Johannes Weiner wrote:
> On Mon, Feb 03, 2014 at 02:33:13PM +0100, Michal Hocko wrote:
> > On Thu 30-01-14 12:29:06, Johannes Weiner wrote:
> > > On Tue, Dec 17, 2013 at 04:45:29PM +0100, Michal Hocko wrote:
[...]
> > > > In order to make this raceless we would need to hold rcu_read_lock since
> > > > css_tryget until res_counter_charge. This is not so easy unfortunately
> > > > because mem_cgroup_do_charge might sleep so we would need to do drop rcu
> > > > lock and do css_tryget tricks after each reclaim.
> > >
> > > Yes, why not?
> >
> > Although css_tryget is cheap these days I thought that a simple flag
> > check would be even heaper in this hot path. Changing the patch to use
> > css_tryget rather than offline check is trivial if you really think it
> > is better?
>
> You already changed it to do css_tryget() on every single charge.
Fair point
Thanks!
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2014-02-03 16:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-17 15:45 [RFC] memcg: some charge path cleanups + css offline vs. charge race fix Michal Hocko
2013-12-17 15:45 ` [RFC 1/5] memcg: cleanup charge routines Michal Hocko
2014-01-30 17:18 ` Johannes Weiner
2014-02-03 13:20 ` Michal Hocko
2014-02-03 15:51 ` Johannes Weiner
2014-02-03 16:41 ` Michal Hocko
2013-12-17 15:45 ` [RFC 2/5] memcg: move stock charge into __mem_cgroup_try_charge_memcg Michal Hocko
2013-12-17 15:45 ` [RFC 3/5] memcg: mm == NULL is not allowed for mem_cgroup_try_charge_mm Michal Hocko
2013-12-17 15:45 ` [RFC 4/5] memcg: make sure that memcg is not offline when charging Michal Hocko
2014-01-30 17:29 ` Johannes Weiner
2014-02-03 13:33 ` Michal Hocko
2014-02-03 16:18 ` Johannes Weiner
2014-02-03 16:44 ` Michal Hocko [this message]
2013-12-17 15:45 ` [RFC 5/5] Revert "mm: memcg: fix race condition between memcg teardown and swapin" Michal Hocko
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