linux-kernel - Re: [PATCH] xfs: do not pass unused params to xfs_flush

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Message-Id: <200804221057.33324.vda.linux@googlemail.com>
Date:	Tue, 22 Apr 2008 10:57:33 +0200
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Eric Sandeen <sandeen@...deen.net>
Cc:	David Chinner <dgc@....com>, Adrian Bunk <bunk@...nel.org>,
	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: do not pass unused params to xfs_flush_pages

On Tuesday 22 April 2008 05:15, Eric Sandeen wrote:
> Denys Vlasenko wrote:
> > Hi David,
> > 
> > xfs_flush_pages() does not use some of its parameters, namely:
> > first, last and fiops.
> > 
> > This patch removes these parameters from all callsites.
> > 
> > Code size difference on 32-bit x86:
> > 
> >    text    data     bss     dec     hex filename
> >  390739    2748    1708  395195   607bb linux-2.6-xfs1-TEST/fs/xfs/xfs.o
> >  390567    2748    1708  395023   6070f linux-2.6-xfs2-TEST/fs/xfs/xfs.o
> > 
> > Compile-tested only.
> 
> FWIW this one actually does not seem to reduce stack usage anywhere.

I hope this will not deteriorate into a contest whether
every particular patch reduces stack usage or not, but:

You do not see reduced stack usage in "make checkstack",
because "make checkstack" shows only stack usage caused by
local variables (it analyses sub %esp,NN instructions which
make room for them). Parameters also take up stack, but
they are pushed on stack with push instruction,
and so are invisible in "make checkstack" output.
--
vda
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