Re: [PATCH 4/4] kstat: modify kstat_irqs_legacy to be variable sized

Mike Travis
2009-01-11T17:48:41Z

Mike Travis wrote:
> 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

I'll push this to my cpus4096-for-ingo.git tree:

Subject: irq: fix initialization of legacy kstat irqs

Impact: fix bug with legacy kstat irqs

The sectioning of the allocated kstat_irqs_legacy should use nr_cpu_ids
instead of NR_IRQS_LEGACY.

Thanks to Yinghai for pointing this out.

Signed-off-by: Mike Travis <travis@sgi.com>
---
kernel/irq/handle.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-2.6-for-ingo.orig/kernel/irq/handle.c
+++ linux-2.6-for-ingo/kernel/irq/handle.c
@@ -155,7 +155,7 @@ int __init early_irq_init(void)

for (i = 0; i < legacy_count; i++) {
desc[i].irq = i;
- desc[i].kstat_irqs = kstat_irqs_legacy + i * NR_IRQS_LEGACY;
+ desc[i].kstat_irqs = kstat_irqs_legacy + i * nr_cpu_ids;
lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
init_alloc_desc_masks(&desc[i], 0, true);
irq_desc_ptrs[i] = desc + i;