Re: [RFC PATCH v3 0/3] x86/perf/amd: AMD PMC counters and NMI latency

From: Vince Weaver
Date: Tue Apr 02 2019 - 11:28:39 EST

On Tue, 2 Apr 2019, Cyrill Gorcunov wrote:
> On Tue, Apr 02, 2019 at 03:03:02PM +0200, Peter Zijlstra wrote:
> > I have vague memories of the P4 thing crashing with Vince's perf_fuzzer,
> > but maybe I'm wrong.
> No, you're correct. p4 was crashing many times before we manage to make
> it more-less stable. The main problem though that to find working p4 box
> is really a problem.

I do have some a functioning p4 system I can test on.
I can easily run the fuzzer and report crashes, but I only have limited
time/skills to actually fix the problems it turns up.

One nice thing is that as of Linux 5.0 *finally* the fuzzer can run
indefinitely on most modern Intel chips without crashing (still triggers a
few warnings). So finally we have the ability to tell when a new crash is
a regression and potentially can bisect it. Although obviously this
doesn't necessarily apply to the p4.

I do think the number of people trying to run perf on a p4 is probably
pretty small these days.