Re: [PATCH] perf, x86: try to handle unknown nmis with running perfctrs

Huang Ying
2010-08-11T03:19:45Z

On Wed, 2010-08-11 at 04:48 +0800, Don Zickus wrote:
> > From d2739578199d881ae6a9537c1b96a0efd1cdea43 Mon Sep 17 00:00:00 2001
> > From: Robert Richter <robert.richter@amd.com>
> > Date: Thu, 5 Aug 2010 16:19:59 +0200
> > Subject: [PATCH] perf, x86: try to handle unknown nmis with running perfctrs
>
> On top of Robert's patch:
> (compiled tested only because I don't have a fancy button to trigger
> unknown nmis)

You can trigger unknown NMIs via apic->send_IPI_mask(cpu_mask,
NMI_VECTOR).

How about the algorithm as follow:

int perf_event_nmi_handler()
{
...
switch (cmd) {
case DIE_NMIUNKNOWN:
if (per_cpu(perfctr_prev_handled) > 1
&& rdtsc() - per_cpu(perfctr_handled_timestamp) < 1000)
return NOTIFY_STOP;
else
return NOTIFY_DONE;
}
...
handled = x86_pmu.handle_irq(regs);
per_cpu(perfctr_prev_handled) = per_cpu(perfctr_handled);
per_cpu(perfctr_handled) = handled;
if (handled) {
per_cpu(perfctr_handled_timestamp) = rdtsc();
return NOTIFY_STOP;
} else
return NOTIFY_DONE;
}

Best Regards,
Huang Ying