From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [Intel-gfx] [PATCH] [RFC] mm/shrinker: Add a shrinker flag to always shrink a bit Date: Thu, 19 Sep 2013 09:52:28 +1000 Message-ID: <20130918235228.GG9901@dastard> References: <1379495401-18279-1-git-send-email-daniel.vetter@ffwll.ch> <5239829F.4080601@t-online.de> <20130918203822.GA4330@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <20130918203822.GA4330@dastard> Sender: owner-linux-mm@kvack.org To: Knut Petersen Cc: Daniel Vetter , Linux MM , Rik van Riel , Intel Graphics Development , Johannes Weiner , LKML , DRI Development , Michal Hocko , Mel Gorman , Glauber Costa , Andrew Morton , Linus Torvalds List-Id: intel-gfx@lists.freedesktop.org [my keyboard my be on the fritz - it's not typing what I'm thinking...] On Thu, Sep 19, 2013 at 06:38:22AM +1000, Dave Chinner wrote: > On Wed, Sep 18, 2013 at 12:38:23PM +0200, Knut Petersen wrote: > > On 18.09.2013 11:10, Daniel Vetter wrote: > >=20 > > Just now I prepared a patch changing the same function in vmscan.c > > >Also, this needs to be rebased to the new shrinker api in 3.12, I > > >simply haven't rolled my trees forward yet. > >=20 > > Well, you should. Since commit 81e49f shrinker->count_objects might = be > > set to SHRINK_STOP, causing shrink_slab_node() to complain loud and o= ften: > >=20 > > [ 1908.234595] shrink_slab: i915_gem_inactive_scan+0x0/0x9c negative = objects to delete nr=3D-xxxxxxxxx > >=20 > > The kernel emitted a few thousand log lines like the one quoted above= during the > > last few days on my system. > >=20 > > >diff --git a/mm/vmscan.c b/mm/vmscan.c > > >index 2cff0d4..d81f6e0 100644 > > >--- a/mm/vmscan.c > > >+++ b/mm/vmscan.c > > >@@ -254,6 +254,10 @@ unsigned long shrink_slab(struct shrink_control= *shrink, > > > total_scan =3D max_pass; > > > } > > >+ /* Always try to shrink a bit to make forward progress. */ > > >+ if (shrinker->evicts_to_page_lru) > > >+ total_scan =3D max_t(long, total_scan, batch_size); > > >+ > > At that place the error message is already emitted. > > > /* > > > * We need to avoid excessive windup on filesystem shrinkers > > > * due to large numbers of GFP_NOFS allocations causing the > >=20 > > Have a look at the attached patch. It fixes my problem with the erron= eous/misleading > > error messages, and I think it=B4s right to just bail out early if SH= RINK_STOP is found. > >=20 > > Do you agree ? >=20 > No, that's wrong. ->count_objects should never ass SHRINK_STOP. *pass > Indeed, it should always return a count of objects in the cache, > regardless of the context.=20 >=20 > SHRINK_STOP is for ->scan_objects to tell the shrinker it can make *can't > any progress due to the context it is called in. This allows the > shirnker to defer the work to another call in a different context. > However, if ->count-objects doesn't return a count, the work that > was supposed to be done cannot be deferred, and that is what *why > ->count_objects should always return the number of objects in the > cache. Cheers, Dave. --=20 Dave Chinner david@fromorbit.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org