linux-kernel - Re: [PATCH 1/2] vmscan: fix initial shrinker size handling

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Message-ID: <20110822232257.GT3162@dastard>
Date:	Tue, 23 Aug 2011 09:22:57 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] vmscan: fix initial shrinker size handling

On Mon, Aug 22, 2011 at 02:17:21PM +0300, Konstantin Khlebnikov wrote:
> Shrinker function can returns -1, it means it cannot do anything without a risk of deadlock.
> For example prune_super() do this if it cannot grab superblock refrence, even if nr_to_scan=0.
> Currenly we interpret this like ULONG_MAX size shrinker, evaluate total_scan according this,
> and next time this shrinker can get really big pressure. Let's skip such shrinkers instead.
> 
> Also make total_scan signed, otherwise check (total_scan < 0) below never works.

I've got a patch set I am going to post out today that makes this
irrelevant.

The patch set splits the shrinker api into 2 callbacks - a "count
objects" callback and an "scan objects" callback, getting rid of
this messy "pass nr-to_scan == 0 to count objects" wart altogether.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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