Messages in this thread | | | Date | Tue, 4 Sep 2012 11:32:31 +0200 | From | Alexander Gordeev <> | Subject | Re: [PATCH v2 -tip 1/5] x86, MSI: Support multiple MSIs in presense of IRQ remapping |
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On Mon, Sep 03, 2012 at 11:53:39AM -0700, Yinghai Lu wrote: > On Mon, Sep 3, 2012 at 2:17 AM, Alexander Gordeev <agordeev@redhat.com> wrote: > 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,) > ....
Indeed. Will do.
> BTW, in short, how much performance benefits for adding 500 lines code?
Unfortunatelly, I do not have a short answer here. There are three types of performance this series deals with - I'll try to summarize:
- devices - 3 SATA HDDs generate roughly one interrupt every 273 us while it get handled in less than 5 us. So there is/could be no increase here;
- the hardware context interrupt handler - its performance dropped 2.5 times (little bit more in fact) at the expense of increase of 1.3 times in overall interrupt handling time (hardware context + threaded context);
- overall system performance - I *assume* it should increase, because: (a) AHCI interrupt handlers keep local interrupts disabled 2.5 times less (b) separate AHCI IRQs become subjects of IRQ balancing (c) threaded handlers are per-device, per-CPU (well, up to irqbalanced) and executed with local interrupts enabled;
-- Regards, Alexander Gordeev agordeev@redhat.com
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