linux-kernel - Re: [PATCH 4/4] kstat: modify kstat_irqs

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Message-ID: <49697646.6000701@sgi.com>
Date:	Sat, 10 Jan 2009 20:32:06 -0800
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Yinghai Lu <yinghai@...nel.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] kstat: modify kstat_irqs_legacy to be variable sized

Ingo Molnar wrote:
> * Mike Travis <travis@....com> wrote:
...
>>>> Allocate kstat_irqs_legacy based on nr_cpu_ids to deal with this
>>>> memory usage bump when NR_CPUS bumped from 128 to 4096:
>>>>
>>>>      8192   +253952    262144 +3100%  kstat_irqs_legacy(.bss)
>>>>
...
>>>> +	/* allocate based on nr_cpu_ids */
>>>> +	kstat_irqs_legacy = alloc_bootmem(NR_IRQS_LEGACY * nr_cpu_ids *
>>>> +					  sizeof(int));
...
>>> btw., while at it - dont we want to upgrade this to a 'long' (in a 
>>> separate commit)? Having more than 4 billion irqs after bootup is easily 
>>> possible.

Looking at this more closely, it seems it would be better to per_cpu_alloc
the legacy kstat_irqs as that would place the value being incremented on the
node of the cpu doing the incrementing. 

This, of course, would need the early per_cpu_alloc (in bootmem) that
the new cpu_alloc changes from Christoph and Rusty is providing.

Thanks,
Mike
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