linux-kernel - Re: [PATCH -mm] vmscan: move reclaim_state handling to shrink

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Message-ID: <20150115075610.GF11264@esperanza>
Date:	Thu, 15 Jan 2015 10:56:10 +0300
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mm] vmscan: move reclaim_state handling to shrink_slab

On Wed, Jan 14, 2015 at 03:34:49PM -0800, Andrew Morton wrote:
> On Wed, 14 Jan 2015 16:55:36 +0300 Vladimir Davydov <vdavydov@...allels.com> wrote:
> > This patch also makes shrink_slab() return the number of reclaimed slab
> > pages (obtained from reclaim_state) instead of the number of reclaimed
> > objects, because the latter is not of much use - it was only checked by
> > drop_slab() to decide whether it should continue reclaim or abort. The
> > number of reclaimed pages is more appropriate, because it also can be
> > used by shrink_zone() to accumulate scan_control->nr_reclaimed.
> 
> Not sure that this is a good change.  If shrink_slab() managed to free
> some objects but didn't free any pages then that's a good sign that
> additional calls to shrink_slab() *will* free some pages.  With this
> change, drop_slab_node() can give up too early.

Fair enough. We'd better leave the return value intact then. I think we
should add an additional argument to add the number of reclaimed slab
pages to, as I intended to do initially. Will resend.

Thanks,
Vladimir
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