linux-kernel - Re: [RFC][PATCH] perf: Rewrite enabled/running timekeeping

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Date:   Fri, 1 Sep 2017 17:03:52 -0400 (EDT)
From:   Vince Weaver <vince@...ter.net>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...el.com>,
        Dmitri Prokhorov <Dmitry.Prohorov@...el.com>,
        Valery Cherepennikov <valery.cherepennikov@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Stephane Eranian <eranian@...gle.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC][PATCH] perf: Rewrite enabled/running timekeeping

On Thu, 31 Aug 2017, Peter Zijlstra wrote:

> So the below completely rewrites timekeeping (and probably breaks
> world) but does away with the need to touch events that don't get
> scheduled.
> 
> Esp the cgroup stuff is entirely untested since I simply don't know how
> to operate that. I did run Vince's tests on it, and I think it doesn't
> regress, but I'm near a migraine so I can't really see straight atm.
> 
> Vince, Stephane, could you guys have a peek?

I have to admit that I *always* got lost trying to figure out the old 
so I might not be the best person to review the changes.

I did try running the perf_event_tests on a few machines and they all pass.

I also ran the PAPI tests and a few of the multiplexing tests fail about 
10% of the time but I think they also fail 10% of the time with the old 
code too.  I need to figure out why that's happening but it's likely a 
PAPI issue not a kernel one.

Vince