Re: [lkp] [x86/MSI] 52f518a3a7c: -30.5% netperf.Throughput_tps

Jiang Liu
2015-06-16T02:09:41Z

On 2015/6/16 1:52, Thomas Gleixner wrote:
> On Mon, 15 Jun 2015, Huang Ying wrote:
>
>> FYI, we noticed the below changes on
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>> commit 52f518a3a7c2f80551a38d38be28bc9f335e713c ("x86/MSI: Use hierarchical irqdomains to manage MSI interrupts")
>>
>
> I really appreciate this testing effort, but the information provided
> is not really helpful.
>
> I asked this before. Can you pretty please, upload ALL relevant
> information (.config, full dmesg, below stats, /proc/interrupts ...)
> to some place where everyone interested can download them?
>
> Then themail contains a useful link instead of 200k waste of network bandwidth.

Hi Ying and Thomas,
I guess this report discloses a regression in hierarchy
irqdomain, and which should have been fixed by the patch posted at:
lkml.org/lkml/2015/6/1/80
The root cause is that, with hierarchy irqdomain enabled,
there are multiple irq_data associated with one irq. And function
irq_move_irq() on x86 uses a wrong copy of irq_data to check
whether there's pending irq migration operation. So all irq migration
/set_affinity operations will get pending for ever. This may
affect network performance due to interrupt load balance issue.
And the patch set posted at
www.gossamer-threads.com/lists/linux/kernel/2185533
should have solved all such regressions.

Thanks!
Gerry

>
> Thanks,
>
> tglx
>