netdev - Re: [PATCH 12/30] mm: memory reserve management

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Message-Id: <1217263769.15724.32.camel@calx>
Date:	Mon, 28 Jul 2008 11:49:29 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	netdev@...r.kernel.org, trond.myklebust@....uio.no,
	Daniel Lezcano <dlezcano@...ibm.com>,
	Neil Brown <neilb@...e.de>, cl@...ux-foundation.org
Subject: Re: [PATCH 12/30] mm: memory reserve management

On Mon, 2008-07-28 at 13:06 +0300, Pekka Enberg wrote:
> We're trying to get rid of kfree() so I'd __kfree_reserve() could to
> mm/sl?b.c. Matt, thoughts?

I think you mean ksize there. My big issue is that we need to make it
clear that ksize pairs -only- with kmalloc and that
ksize(kmem_cache_alloc(...)) is a categorical error. Preferably, we do
this by giving it a distinct name, like kmalloc_size(). We can stick an
underbar in front of it to suggest you ought not be using it too.

> > +	/*
> > +	 * ksize gives the full allocated size vs the requested size we
> used to
> > +	 * charge; however since we round up to the nearest power of two,
> this
> > +	 * should all work nicely.
> > +	 */

SLOB doesn't do this, of course. But does that matter? I think you want
to charge the actual allocation size to the reserve in all cases, no?
That probably means calling ksize() on both alloc and free.

-- 
Mathematics is the supreme nostalgia of our time.

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