linux-kernel - Re: [PATCH] module: kzalloc mod->ref

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Message-ID: <496DBB25.9040101@rsk.demon.co.uk>
Date:	Wed, 14 Jan 2009 10:15:01 +0000
From:	richard kennedy <richard@....demon.co.uk>
To:	Kyle McMartin <kyle@...radead.org>
CC:	rusty@...tcorp.com.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] module: kzalloc mod->ref

Kyle McMartin wrote:
> From: Kyle McMartin <kyle@...hat.com>
> 
> Dynamically allocate mod->ref instead of fixing it in the struct module.
> Reduces on disk space wasted in the module .ko, and kills a loop
> initializing the local_t it contains since we can just kzalloc it.
> 
> This matters when we're talking about large NR_CPUS.
> 
> Signed-off-by: Kyle McMartin <kyle@...hat.com>
> ---
> The patch removing cacheline_aligned from struct module_ref should be
> applied as well to cut down on the amount of memory we allocate. This
> patch makes a nice stopgap until we have per_cpu module references.
> 
> cheers, Kyle
> 
Hi Kyle,

As module_get/ put use module_ref as a per_cpu variable won't removing
the cacheline_aligned be a performance hit due to cacheline sharing on
machines with reasonable or small number of cpus?

(some of the network code seems to call module_get/put a lot!)

regards
Richard
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