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Date: Tue, 11 Nov 2008 23:15:50 +0100
From: Eric Dumazet <dada1@...mosbay.com>
To: Takashi Iwai <tiwai@...e.de>
CC: Rusty Russell <rusty@...tcorp.com.au>,
Andreas Gruenbacher <agruen@...e.de>,
Jan Blunck <jblunck@...e.de>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Mike Travis <travis@....com>
Subject: Re: [PATCH] Allocate module.ref array dynamically
Eric Dumazet a écrit :
> Takashi Iwai a écrit :
>> Hi,
>>
>> we found that the kernel module sizes and memory footprints
>> grow drastically when NR_CPUS is high. For example, with
>> NR_CPUS=4096, SUSE kernel packages weigh over 500MB (even w/o debug
>> info).
>>
>> A part of the reason is the fixed size array in struct module.
>> The patch below fixes the problem by allocating it dynamically.
>> With the patch, the size can go down to 20MB.
>>
>>
>> Any comments/suggestions appreciated.
>>
>
> Many attempts were done on this area on the past.
Forgot to include a link to previous attempt : http://lkml.org/lkml/2008/5/15/402
>
> Your patch has the drawback of using kcalloc(), while previously,
> module_ref
> space was allocated with vmalloc().
>
> After a while, a machine could have a lot of vmalloc() space available,
> but not enough
> physically contiguous space to fullfill a kmalloc(large_area) call.
>
> So a module load could fail, while previous code could load module.
>
> I believe Mike Travis has a better patch for this problem, partly using
> new percpu allocator.
>
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