linux-kernel - Re: [Intel-gfx] [PATCH] [RFC] mm/shrinker: Add a shrinker flag to always shrink a bit

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Message-ID: <CAKMK7uGR7HtMLgu2-tvfTm+W=_gndVJ7QPcf0okFcKX6Htd61Q@mail.gmail.com>
Date:	Thu, 19 Sep 2013 08:57:04 +0200
From:	Daniel Vetter <daniel.vetter@...ll.ch>
To:	Dave Chinner <david@...morbit.com>
Cc:	Knut Petersen <Knut_Petersen@...nline.de>,
	Linux MM <linux-mm@...ck.org>, Rik van Riel <riel@...hat.com>,
	Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	DRI Development <dri-devel@...ts.freedesktop.org>,
	Michal Hocko <mhocko@...e.cz>, Mel Gorman <mgorman@...e.de>,
	Glauber Costa <glommer@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [Intel-gfx] [PATCH] [RFC] mm/shrinker: Add a shrinker flag to
 always shrink a bit

On Wed, Sep 18, 2013 at 10:38 PM, Dave Chinner <david@...morbit.com> wrote:
> No, that's wrong. ->count_objects should never ass SHRINK_STOP.
> Indeed, it should always return a count of objects in the cache,
> regardless of the context.
>
> SHRINK_STOP is for ->scan_objects to tell the shrinker it can make
> 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
> ->count_objects should always return the number of objects in the
> cache.

So we should rework the locking in the drm/i915 shrinker to be able to
always count objects? Thus far no one screamed yet that we're not
really able to do that in all call contexts ...

So should I revert 81e49f or will the early return 0; completely upset
the core shrinker logic?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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