linux-kernel - Re: [PATCH] memcg: Add memory.pressure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130213071503.GA20543@lizard.gateway.2wire.net>
Date:	Tue, 12 Feb 2013 23:15:03 -0800
From:	Anton Vorontsov <anton@...msg.org>
To:	Greg Thelen <gthelen@...gle.com>
Cc:	cgroups@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	Mel Gorman <mgorman@...e.de>,
	Glauber Costa <glommer@...allels.com>,
	Michal Hocko <mhocko@...e.cz>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Leonid Moiseichuk <leonid.moiseichuk@...ia.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	John Stultz <john.stultz@...aro.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	patches@...aro.org, kernel-team@...roid.com
Subject: Re: [PATCH] memcg: Add memory.pressure_level events

Hi Greg,

Thanks for taking a look!

On Tue, Feb 12, 2013 at 10:42:51PM -0800, Greg Thelen wrote:
[...]
> > +static unsigned long vmpressure_calc_level(unsigned int win,
> > +					   unsigned int s, unsigned int r)
> 
> Should seems like the return type of this function should be enum
> vmpressure_levels?  If yes, then the 'return 0' below should be
> VMPRESSURE_LOW.  And it would be nice if there was a little comment
> describing the meaning of the win, s, and r parameters.  The "We
> calculate ..." comment below makes me think that win is the number of
> pages scanned, which makes me wonder what the s param is.

Got it, will make it clearer.

[...]
> > +static bool vmpressure_event(struct vmpressure *vmpr,
> > +			     unsigned long s, unsigned long r)
> > +{
> > +	struct vmpressure_event *ev;
> > +	int level = vmpressure_calc_level(vmpressure_win, s, r);
> > +	bool signalled = 0;
> s/bool/int/

Um... I surely can do this, but why do you think it is a good idea?

> > +
> > +	mutex_lock(&vmpr->events_lock);
> > +
> > +	list_for_each_entry(ev, &vmpr->events, node) {
> > +		if (level >= ev->level) {
> > +			eventfd_signal(ev->efd, 1);
> > +			signalled++;
> > +		}
> > +	}
> > +
> > +	mutex_unlock(&vmpr->events_lock);
> > +
> > +	return signalled;

[...]
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1982,6 +1982,10 @@ static void shrink_zone(struct zone *zone, struct scan_control *sc)
> >  			}
> >  			memcg = mem_cgroup_iter(root, memcg, &reclaim);
> >  		} while (memcg);
> > +
> > +		vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
> > +			   sc->nr_scanned - nr_scanned, nr_reclaimed);
> 
> (sc->nr_scanned - nr_scanned) is the number of pages scanned in above
> while loop but nr_reclaimed is the starting position of the reclaim
> counter before the loop.  It seems like you want:
> 	vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
> 		   sc->nr_scanned - nr_scanned, 
> 		   sc->nr_reclaimed - nr_reclaimed);

Yeah, right you are. There actually was a merge conflict when I rebased my
patch onto linux-next, and it seems that I overlooked that the logic has
changed. So we might get a bit distorted pressure because of that.

Thanks for catching this!

Anton
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/