linux-kernel - Re: [patch 3/8] mm: memcg: clean up fault accounting

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Message-ID: <20111124095124.GG6843@cmpxchg.org>
Date:	Thu, 24 Nov 2011 10:51:24 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <bsingharora@...il.com>, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 3/8] mm: memcg: clean up fault accounting

On Thu, Nov 24, 2011 at 10:33:49AM +0100, Michal Hocko wrote:
> On Wed 23-11-11 16:42:26, Johannes Weiner wrote:
> > From: Johannes Weiner <jweiner@...hat.com>
> > 
> > The fault accounting functions have a single, memcg-internal user, so
> > they don't need to be global.  In fact, their one-line bodies can be
> > directly folded into the caller.  
> 
> At first I thought that this doesn't help much because the generated
> code should be exactly same but thinking about it some more it makes
> sense.
> We should have a single place where we account for events. Maybe we
> should include also accounting done in mem_cgroup_charge_statistics
> (this would however mean that mem_cgroup_count_vm_event would have to be
> split). What do you think?

I'm all for unifying all the stats crap into a single place.
Optimally, we should have been able to put memcg hooks below
count_vm_event* but maybe that ship has sailed with PGPGIN/PGPGOUT
having different meanings between memcg and the rest of the system :/

Anything in that direction is improvement, IMO.

> > And since faults happen one at a time, use this_cpu_inc() directly
> > instead of this_cpu_add(foo, 1).
> 
> The generated code will be same but it is easier to read, so agreed.

And it fits within 80 columns :-)

> > Signed-off-by: Johannes Weiner <jweiner@...hat.com>
> 
> Anyway
> Acked-by: Michal Hocko <mhocko@...e.cz>

Thanks.
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