Messages in this thread | | | Date | Mon, 3 Feb 2014 17:44:55 +0100 | From | Michal Hocko <> | Subject | Re: [RFC 4/5] memcg: make sure that memcg is not offline when charging |
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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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