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Date:   Tue, 20 Nov 2018 14:38:54 -0800
From:   Andi Kleen <ak@linux.intel.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Kyle Huey <me@kylehuey.com>, Kan Liang <kan.liang@linux.intel.com>,
        Ingo Molnar <mingo@kernel.org>,
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        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Stephane Eranian <eranian@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vince Weaver <vincent.weaver@maine.edu>, acme@kernel.org,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [REGRESSION] x86, perf: counter freezing breaks rr
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> In fact, I'll argue FREEZE_ON_OVERFLOW is unfixably broken for
> independent counters, because while one counter overflows, we'll stall
> counting on all others until we've handled the PMI.
> 
> Even though the PMI might not be for them and they very much want/need
> to continue counting.

We stop all counters in any case for the PMI. With freeze-on-PMI it just
happens slightly earlier.

-Andi