Re: [PATCH 5/8] x86/apic: Try to spread IRQ vectors to differentpriority levels

From: Suresh Siddha
Date: Thu Jun 07 2012 - 18:26:28 EST


On Thu, 2012-06-07 at 15:15 +0200, Alexander Gordeev wrote:
> When assigning a new vector it is primarially done by adding 8 to the
> previously given out vector number. Hence, two consequently allocated
> vector numbers would likely fall into the same priority level. Try to
> spread vector numbers to different priority levels better by changing
> the step from 8 to 16.
>

Acked-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>

> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>
> ---
> arch/x86/kernel/apic/io_apic.c | 7 +++----
> 1 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index 74c5697..05af3d3 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -1112,7 +1112,7 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
> * 0x80, because int 0x80 is hm, kind of importantish. ;)
> */
> static int current_vector = FIRST_EXTERNAL_VECTOR + VECTOR_OFFSET_START;
> - static int current_offset = VECTOR_OFFSET_START % 8;
> + static int current_offset = VECTOR_OFFSET_START % 16;
> unsigned int old_vector;
> int cpu, err;
> cpumask_var_t tmp_mask;
> @@ -1148,10 +1148,9 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
> vector = current_vector;
> offset = current_offset;
> next:
> - vector += 8;
> + vector += 16;
> if (vector >= first_system_vector) {
> - /* If out of vectors on large boxen, must share them. */
> - offset = (offset + 1) % 8;
> + offset = (offset + 1) % 16;
> vector = FIRST_EXTERNAL_VECTOR + offset;
> }
> if (unlikely(current_vector == vector))
> --
> 1.7.7.6
>


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