Re: [PATCH 5/5] Memory controller soft limit reclaim on contention (v7)

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-20 13:06:30]:

> On Thu, 19 Mar 2009 22:27:52 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 
> > Feature: Implement reclaim from groups over their soft limit
> > 
> > From: Balbir Singh <balbir@linux.vnet.ibm.com>
> > 
> > Changelog v7...v6
> > 1. Refactored out reclaim_options patch into a separate patch
> > 2. Added additional checks for all swap off condition in
> >    mem_cgroup_hierarchical_reclaim()
> 
> > -	did_some_progress = try_to_free_pages(zonelist, order, gfp_mask);
> > +	/*
> > +	 * Try to free up some pages from the memory controllers soft
> > +	 * limit queue.
> > +	 */
> > +	did_some_progress = mem_cgroup_soft_limit_reclaim(zonelist, gfp_mask);
> > +	if (order || !did_some_progress)
> > +		did_some_progress += try_to_free_pages(zonelist, order,
> > +							gfp_mask);
> >  
> 
> Anyway, my biggest concern is here, always.
> 
>         By this.
>           if (order > 1), try_to_free_pages() is called twice.

try_to_free_mem_cgroup_pages and try_to_free_pages() are called

>         Hmm...how about


> 
>         if (!pages_reclaimed && !(gfp_mask & __GFP_NORETRY)) { # this is the first loop or noretry
>                did_some_progress = mem_cgroup_soft_limit_reclaim(zonelist, gfp_mask);

OK, I see what you mean.. but the cost of the
mem_cgroup_soft_limit_reclaim() is really a low overhead call, which
will bail out very quickly if nothing is over their soft limit.
Even if we retry, we do a simple check for soft-limit-reclaim, if
there is really something to be reclaimed, we reclaim from there
first.

>                if (!did_some_progress)
>                     did_some_progress = try_to_free_pages(zonelist, order, gfp_mask);
>         }else
>                     did_some_progress = try_to_free_pages(zonelist, order, gfp_mask);
> 
> 
>         maybe a bit more concervative.
> 
> 
>         And I wonder "nodemask" should be checked or not..
>         softlimit reclaim doesn't seem to work well with nodemask...

Doesn't the zonelist take care of nodemask?


-- 
	Balbir

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