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

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Message-ID: <alpine.DEB.2.21.1904021050090.15645@pianoman.cluster.toy>
Date:   Tue, 2 Apr 2019 10:53:38 -0400 (EDT)
From:   Vince Weaver <vince@...ter.net>
To:     Cyrill Gorcunov <gorcunov@...il.com>
cc:     Peter Zijlstra <peterz@...radead.org>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiri Olsa <jolsa@...hat.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [RFC PATCH v3 0/3] x86/perf/amd: AMD PMC counters and NMI
 latency

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.

Vince