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Date: Sun, 11 Jan 2009 09:40:49 -0800
From: Mike Travis <travis@sgi.com>
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To: Yinghai Lu <yinghai@kernel.org>
CC: Ingo Molnar <mingo@redhat.com>, Rusty Russell <rusty@rustcorp.com.au>,
       Jack Steiner <steiner@sgi.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/4] kstat: modify kstat_irqs_legacy to be variable sized
References: <20090110223818.459493000@polaris-admin.engr.sgi.com>	 <20090110223819.033438000@polaris-admin.engr.sgi.com> <86802c440901102301n5a7bb98ajd44a31ab32ddb726@mail.gmail.com>
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Yinghai Lu wrote:
> On Sat, Jan 10, 2009 at 2:38 PM, Mike Travis <travis@sgi.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@sgi.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;
> 
> YH

Hmm, thanks!  (I wonder why I wanted it the other way?  Oh well.)

I'll make an append patch to fix it.

Thanks,
Mike