linux-kernel - Re: [PATCH] Cleanup and kernelify shrinker registration (rc5-mm2)

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Date:	Tue, 03 Apr 2007 14:45:02 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, xfs-masters@....sgi.com,
	reiserfs-dev@...esys.com
Subject: Re: [PATCH] Cleanup and kernelify shrinker registration (rc5-mm2)

On Mon, 2007-04-02 at 20:58 -0700, Andrew Morton wrote:
> On Tue, 03 Apr 2007 13:44:45 +1000 Rusty Russell <rusty@...tcorp.com.au> wrote:
> 
> > 
> > I can never remember what the function to register to receive VM pressure
> > is called.  I have to trace down from __alloc_pages() to find it.
> > 
> > It's called "set_shrinker()", and it needs Your Help.
> > 
> > New version:
> > 1) Don't hide struct shrinker.  It contains no magic.
> > 2) Don't allocate "struct shrinker".  It's not helpful.
> > 3) Call them "register_shrinker" and "unregister_shrinker".
> > 4) Call the function "shrink" not "shrinker".
> > 5) Rename "nr_to_scan" argument to "nr_to_free".
> 
> No, it is actually the number to scan.  This is >= the number of freed
> objects.
> 
> This is because, for better of for worse, the VM tries to balance the
> scanning rate of the various caches, not the reclaiming rate.

Err, ok, I completely missed that distinction.

Does that mean the to function correctly every user needs some internal
cursor so it doesn't end up scanning the first N entries over and over?

Rusty.

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