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

Mike Travis
2009-01-10T23:08:20Z

Ingo Molnar wrote:
> * 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;
>> lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
>> init_alloc_desc_masks(&desc[i], 0, true);
>> irq_desc_ptrs[i] = desc + i;
>
> 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.
>
> Ingo

Yes, I can do that. There are two places where it allocated, both for
legacy and dynamically added desc's.

You want basically this, yes?

--- linux-2.6-for-ingo.orig/include/linux/irq.h
+++ linux-2.6-for-ingo/include/linux/irq.h
@@ -162,7 +162,7 @@ struct irq_desc {
unsigned int irq;
#ifdef CONFIG_SPARSE_IRQ
struct timer_rand_state *timer_rand_state;
- unsigned int *kstat_irqs;
+ unsigned long *kstat_irqs;
# ifdef CONFIG_INTR_REMAP
struct irq_2_iommu *irq_2_iommu;
# endif

Thanks,
Mike