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

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Date:	Sun, 11 Jan 2009 09:50:07 -0800
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	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:
> * Yinghai Lu <yinghai@...nel.org> wrote:
> 
>> On Sat, Jan 10, 2009 at 2:38 PM, Mike Travis <travis@....com> wrote:
>>> Impact: reduce memory usage.
>>>
>>> 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)
>>>
>>> This is only when CONFIG_SPARSE_IRQS=y.
>>>
>>> Signed-off-by: Mike Travis <travis@....com>
>>> ---
>>>  kernel/irq/handle.c |    9 ++++++---
>>>  1 file changed, 6 insertions(+), 3 deletions(-)
>>>
>>> --- linux-2.6-for-ingo.orig/kernel/irq/handle.c
>>> +++ linux-2.6-for-ingo/kernel/irq/handle.c
>>> @@ -124,8 +124,7 @@ static struct irq_desc irq_desc_legacy[N
>>>        }
>>>  };
>>>
>>> -/* FIXME: use bootmem alloc ...*/
>>> -static unsigned int kstat_irqs_legacy[NR_IRQS_LEGACY][NR_CPUS];
>>> +static unsigned int *kstat_irqs_legacy;
>>>
>>>  int __init early_irq_init(void)
>>>  {
>>> @@ -146,9 +145,13 @@ int __init early_irq_init(void)
>>>        /* allocate irq_desc_ptrs array based on nr_irqs */
>>>        irq_desc_ptrs = alloc_bootmem(nr_irqs * sizeof(void *));
>>>
>>> +       /* allocate based on nr_cpu_ids */
>>> +       kstat_irqs_legacy = alloc_bootmem(NR_IRQS_LEGACY * nr_cpu_ids *
>>> +                                         sizeof(int));
>>> +
>>>        for (i = 0; i < legacy_count; i++) {
>>>                desc[i].irq = i;
>>> -               desc[i].kstat_irqs = kstat_irqs_legacy[i];
>>> +               desc[i].kstat_irqs = kstat_irqs_legacy + i * NR_IRQS_LEGACY;
>> here should be
>>
>> +               desc[i].kstat_irqs = kstat_irqs_legacy + i * nr_cpu_ids;
> 
> indeed - i fixed this in tip/cpus4096.
> 
> 	Ingo

Ahh, I didn't see this.  Thanks Ingo!
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