On Mon, Sep 3, 2012 at 2:17 AM, Alexander Gordeev <agordeev@xxxxxxxxxx> wrote:
> The MSI specification has several constraints in comparison with MSI-X,
> most notable of them is the inability to configure MSIs independently.
> As a result, it is impossible to dispatch interrupts from different
> queues to different CPUs. This is largely devalues the support of
> multiple MSIs in SMP systems.
>
> Also, a necessity to allocate a contiguous block of vector numbers for
> devices capable of multiple MSIs might cause a considerable pressure on
> x86 interrupt vector allocator and could lead to fragmentation of the
> interrupt vectors space.
>
> This patch overcomes both drawbacks in presense of IRQ remapping and
> lets devices take advantage of multiple queues and per-IRQ affinity
> assignments.
>
> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>
> ---
> arch/x86/kernel/apic/io_apic.c | 166 +++++++++++++++++++++++++++++++++++++--
> include/linux/irq.h | 6 ++
> kernel/irq/chip.c | 30 +++++--
> kernel/irq/irqdesc.c | 31 ++++++++
> 4 files changed, 216 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index c265593..5fd2577 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -305,6 +305,11 @@ static int alloc_irq_from(unsigned int from, int node)
> return irq_alloc_desc_from(from, node);
> }
>
> +static int alloc_irqs_from(unsigned int from, unsigned int count, int node)
> +{
> + return irq_alloc_descs_from(from, count, node);
> +}
> +
> static void free_irq_at(unsigned int at, struct irq_cfg *cfg)
> {
> free_irq_cfg(at, cfg);
> @@ -3039,6 +3044,55 @@ int create_irq(void)
> return irq;
> }
>
> +unsigned int create_irqs(unsigned int from, unsigned int count, int node)
> +{
> + struct irq_cfg **cfg;
> + unsigned long flags;
> + int irq, i;
> +
> + if (from < nr_irqs_gsi)
> + from = nr_irqs_gsi;
> +
> + cfg = kzalloc_node(count * sizeof(cfg[0]), GFP_KERNEL, node);
> + if (!cfg)
> + return 0;
> +
> + irq = alloc_irqs_from(from, count, node);
> + if (irq < 0)
> + goto out_cfgs;
> +
> + for (i = 0; i < count; i++) {
> + cfg[i] = alloc_irq_cfg(irq + i, node);
> + if (!cfg[i])
> + goto out_irqs;
> + }
> +
> + raw_spin_lock_irqsave(&vector_lock, flags);
> + for (i = 0; i < count; i++)
> + if (__assign_irq_vector(irq + i, cfg[i], apic->target_cpus()))
> + goto out_vecs;
> + raw_spin_unlock_irqrestore(&vector_lock, flags);
> +
> + for (i = 0; i < count; i++) {
> + irq_set_chip_data(irq + i, cfg[i]);
> + irq_clear_status_flags(irq + i, IRQ_NOREQUEST);
> + }
> +
> + kfree(cfg);
> + return irq;
> +
> +out_vecs:
> + for (; i; i--)
> + __clear_irq_vector(irq + i - 1, cfg[i - 1]);
> + raw_spin_unlock_irqrestore(&vector_lock, flags);
> +out_irqs:
> + for (i = 0; i < count; i++)
> + free_irq_at(irq + i, cfg[i]);
> +out_cfgs:
> + kfree(cfg);
> + return 0;
> +}
> +
You may update create_irq_nr to be __create_irq_nr, and it could take
extra count.
and later have create_irq_nr to be __create_irq_nr(,1,)
and create_irqs to be __create_irq_nr(,count,)
....
BTW, in short, how much performance benefits for adding 500 lines code?
Thanks
Yinghai
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