linux-kernel - Re: mm/slab.c: remove effectively dead code from kmem_cache

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Message-ID: <1328879201.13624.52.camel@jaguar>
Date:	Fri, 10 Feb 2012 15:06:41 +0200
From:	Pekka Enberg <penberg@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	daniel.santos@...ox.com, Daniel Santos <danielfsantos@....net>,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: mm/slab.c: remove effectively dead code from kmem_cache_create

On Thu, 2012-02-09 at 14:39 -0800, Andrew Morton wrote:
> kmem_cache_create() is called extremely rarely, so the performance
> benefit here is negligible.
> 
> We could presumably avoid two of those ifdefs by defining SLAB_RED_ZONE
> and SLAB_STORE_USER to be zero if !defined(DEBUG).  Personally I think
> that's a bit too subtle and would prefer the explicit ifdefs.
> 
> In my x86_64 allnoconfig build the patch reduces slab.o's text size
> from 12859 bytes to 12812.  I'll let Pekka decide if that's worth it ;)

The text savings are worth it but I'd really prefer to see
include/linux/slab.h patched to define debugging flags as zero for
non-CONFIG_SLAB_DEBUG and let GCC eliminate the dead code for us.

			Pekka

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