linux-kernel - Re: [PATCH] Expose sysctls for enabling slab/file

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Message-ID: <20131119201333.GD19762@tassilo.jf.intel.com>
Date:	Tue, 19 Nov 2013 12:13:33 -0800
From:	Andi Kleen <ak@...ux.intel.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Expose sysctls for enabling slab/file_cache interleaving

On Tue, Nov 19, 2013 at 08:11:35PM +0100, Michal Hocko wrote:
> On Tue 19-11-13 19:42:00, Andi Kleen wrote:
> > On Tue, Nov 19, 2013 at 11:42:03AM +0100, Michal Hocko wrote:
> > > On Mon 18-11-13 16:50:22, Andi Kleen wrote:
> > > [...]
> > > > diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
> > > > index cc1b01c..10966f5 100644
> > > > --- a/include/linux/cpuset.h
> > > > +++ b/include/linux/cpuset.h
> > > > @@ -72,12 +72,14 @@ extern int cpuset_slab_spread_node(void);
> > > >  
> > > >  static inline int cpuset_do_page_mem_spread(void)
> > > >  {
> > > > -	return current->flags & PF_SPREAD_PAGE;
> > > > +	return (current->flags & PF_SPREAD_PAGE) ||
> > > > +		sysctl_spread_file_cache;
> > > >  }
> > > 
> > > But this might break applications that explicitly opt out from
> > > spreading.
> > 
> > What do you mean? There's no such setting at the moment.
> > 
> > They can only enable it.
> 
> cpuset_update_task_spread_flag allows disabling both flags. You can do
> so for example via cpuset cgroup controller.

Ok.

So you're saying it should look up the cpuset. I'm reluctant do 
that. It would make this path quite a bit more expensive.

Is it really a big problem to override that setting with
the global sysctl. Seems like sensible semantics for me.

-Andi
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