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

Ingo Molnar
2009-01-11T01:09:11Z

* Mike Travis <travis@sgi.com> wrote:

> 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?

yes - but please also check all that places that use it.

Ingo