Re: [RFC] perf/x86: PMU IRQ handler issues

[Stephane Eranian]

On Wed, May 28, 2014 at 9:55 PM, Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:
>
>> Another explanation is that because we ACK the NMI early, we leave the
>> door open to other interrupts, incl. NIC, and we are interrupting the execution
>
> PMI executes with interrupts off.
>
And that's coming from where?

>> of the PMU IRQ handler, yet that detour is measured in the PMU handler
>> latency, causing more throttling than needed. Is that a plausible scenario too?
>> And if so, I think we need to narrow the window for timing errors, by
>> acking late
>> on all processors and not just HSW.
>
> If you think there's a concrete problem please show an ftrace.
>
> -Andi
> --
> ak@xxxxxxxxxxxxxxx -- Speaking for myself only
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