linux-kernel - Re: [PATCH] xfs: reduce stack usage in xfs_bmap

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Message-ID: <20080428033249.GE103491721@sgi.com>
Date:	Mon, 28 Apr 2008 13:32:49 +1000
From:	David Chinner <dgc@....com>
To:	David Chinner <dgc@....com>
Cc:	Denys Vlasenko <vda.linux@...glemail.com>, xfs@....sgi.com,
	Eric Sandeen <sandeen@...deen.net>,
	Adrian Bunk <bunk@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: reduce stack usage in xfs_bmap_btalloc()

On Mon, Apr 28, 2008 at 09:40:56AM +1000, David Chinner wrote:
> On Sat, Apr 26, 2008 at 04:51:02PM +0200, Denys Vlasenko wrote:
> > Hi David,
> > 
> > This patch reduces xfs_bmap_btalloc() stack usage by 50 bytes
> > by moving part of its body into a helper function.
> 
> Can you please attach your patches inline, Denys (see
> Documentation/SubmittingPatches)?
> 
> > This results in some variables not taking stack space in
> > xfs_bmap_btalloc() anymore.
> > 
> > The helper itself does not call anything stack-deep.
> > Stack-deep call to xfs_alloc_vextent() happen
> > in xfs_bmap_btalloc(), as before.
> 
> I have a set of patches that introduces new functionality into the
> allocator (dynamic allocation policies) that reduces
> xfs_bmap_btalloc() function by 36 bytes (just by chance, I didn't
> design it for this purpose). It breaks it down on functional
> boundaries like Christoph's patch. I'm going to revist that patch
> w.r.t both these patches and see what falls out the bottom...

44 bytes saved in xfs_bmap_btalloc with the same factoring as
Christoph's patch being done. Given that most of this is now
the struct xfs_alloc_arg, I don't think this will be reduced a whole
lot more. I think I might be able to kill the tryagain and isaligned
variables as well which will save another 8 bytes, but I'll leave
that for later....

Good progress, folks.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group
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