linux-kernel - Re: [PATCH] xfs: #define out unused parameters of xfs_bmap_add_free and xfs_btree_read

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Message-ID: <20080422142807.GD16895@cs181133002.pp.htv.fi>
Date:	Tue, 22 Apr 2008 17:28:07 +0300
From:	Adrian Bunk <bunk@...nel.org>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	David Chinner <dgc@....com>, Eric Sandeen <sandeen@...deen.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Shawn Bohrer <shawn.bohrer@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] xfs: #define out unused parameters of
	xfs_bmap_add_free and xfs_btree_read_bufl

On Tue, Apr 22, 2008 at 01:20:54PM +0200, Denys Vlasenko wrote:
> Hi David,
> 
> xfs_bmap_add_free and xfs_btree_read_bufl functions
> use some of their parameters only in some cases
> (e.g. if DEBUG is defined, or on non-Linux OS :)
> 
> This patch removes these parameters using #define hack
> which makes them "disappear" without the need of uglifying
> every callsite with #ifdefs.
> 
> Code size difference on 32-bit x86:
>  393457    2904    2952  399313   617d1 linux-2.6-xfs6-TEST/fs/xfs/xfs.o
>  393441    2904    2952  399297   617c1 linux-2.6-xfs7-TEST/fs/xfs/xfs.o
>...

Elimination of completely unused parameters makes sense, but IMHO using 
such #define hacks for minuscule code size and stack usage advantages is 
not worth it.

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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