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Re: [dm-devel] new dm-bufio

To: xfs@xxxxxxxxxxx, xfs-masters@xxxxxxxxxxx, Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [dm-devel] new dm-bufio
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date: Mon, 29 Aug 2011 14:53:51 -0400 (EDT)
Cc: device-mapper development <dm-devel@xxxxxxxxxx>, Joe Thornber <thornber@xxxxxxxxxx>, "Alasdair G. Kergon" <agk@xxxxxxxxxx>, Mike Snitzer <snitzer@xxxxxxxxxx>
In-reply-to: <20110823185423.GA10936@xxxxxxxxxxxxx>
References: <Pine.LNX.4.64.1108221600510.26651@xxxxxxxxxxxxxxxxxxxxxxxxxxx> <20110823113048.GC5442@ubuntu> <Pine.LNX.4.64.1108231012560.2629@xxxxxxxxxxxxxxxxxxxxxxxxxxx> <20110823185423.GA10936@xxxxxxxxxxxxx>

On Tue, 23 Aug 2011, Christoph Hellwig wrote:

> FYI, the "shrinker" interface in include/linux/shrinker.h is how the
> VM tells subsystems to shrink their memory usage.  It is used for
> various slab caches, and the XFS buffercache in
> fs/xfs/linux-2.6/xfs_buf.c

BTW. shrinker functions from xfs_qm.c - xfs_qm_shake and 
xfs_qm_shake_freelist - look completely bogus. They don't read 
sc->nr_to_scan to determine how many values they should scan (and compare 
it with zero to test if they should scan at all) and they return the 
number of entries freed - the interface specifies that they should return 
the number of entries remaining the in cache.

Mikulas

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