linux-kernel - Re: [patch] mm: oom_kill: revert 3% system memory bonus for privileged tasks

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Message-ID: <20140124040531.GF4407@cmpxchg.org>
Date:	Thu, 23 Jan 2014 23:05:31 -0500
From:	Johannes Weiner <hannes@...xchg.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] mm: oom_kill: revert 3% system memory bonus for
 privileged tasks

On Tue, Jan 21, 2014 at 08:53:07PM -0800, David Rientjes wrote:
> On Thu, 16 Jan 2014, Johannes Weiner wrote:
> 
> > > Unfortunately, I think this could potentially be too much of a bonus.  On 
> > > your same 32GB machine, if a root process is using 18GB and a user process 
> > > is using 14GB, the user process ends up getting selected while the current 
> > > discount of 3% still selects the root process.
> > > 
> > > I do like the idea of scaling this bonus depending on points, however.  I 
> > > think it would be better if we could scale the discount but also limit it 
> > > to some sane value.
> > 
> > I just reverted to the /= 4 because we had that for a long time and it
> > seemed to work.  I don't really mind either way as long as we get rid
> > of that -3%.  Do you have a suggestion?
> > 
> 
> How about simply using 3% of the root process's points so that root 
> processes get some bonus compared to non-root processes with the same 
> memory usage and it's scaled to the usage rather than amount of available 
> memory?
> 
> So rather than points /= 4, we do
> 
> 	if (has_capability_noaudit(p, CAP_SYS_ADMIN))
> 		points -= (points * 3) / 100;
> 
> instead.  Sound good?

Yes, should be okay.

Do you want to send a patch?  Want me to update mine?
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