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

["Yinghai Lu" <yinghai@kernel.org>]

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