From: Andi Kleen <ak@linux.intel.com>
To: Stephane Eranian <eranian@google.com>
Cc: "Liang, Kan" <kan.liang@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
"mingo@redhat.com" <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Jiri Olsa <jolsa@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vince Weaver <vincent.weaver@maine.edu>
Subject: Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86
Date: Mon, 22 May 2017 13:01:44 -0700 [thread overview]
Message-ID: <20170522200144.GE15563@tassilo.jf.intel.com> (raw)
In-Reply-To: <CABPqkBR2A99N+66bw8s6-xZbBtazdEfsWdiaVbL1aT4r0+wkJQ@mail.gmail.com>
>
> > The ref cycles always tick at their frequency, or slower when the system
> > is idling. That means the NMI watchdog can never expire too early,
> > unlike with cycles.
> >
> Just make the period longer, like 30% longer. Take the max turbo factor you can
> get and use that. It is okay if it takes longer of machine with
> smaller max Turbo ratios.
That would be a ticking time bomb. Turbo ratios are likely to grow.
There's no architectural way to get a turbo factor. Even if there
is a model specific MSR it would likely not work in virtualization etc.
You could make the timeout ridiculously large, but even that would
have a small chance of failure.
-Andi
next prev parent reply other threads:[~2017-05-22 20:01 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-19 17:06 [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter kan.liang
2017-05-19 17:06 ` [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86 kan.liang
2017-05-22 12:03 ` Peter Zijlstra
2017-05-22 12:04 ` Peter Zijlstra
2017-05-22 16:58 ` Liang, Kan
2017-05-22 19:24 ` Peter Zijlstra
2017-05-22 18:20 ` Stephane Eranian
2017-05-22 20:01 ` Andi Kleen [this message]
2017-05-22 8:30 ` [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Peter Zijlstra
2017-05-22 18:15 ` Stephane Eranian
2017-05-22 9:19 ` Peter Zijlstra
2017-05-22 12:22 ` Peter Zijlstra
2017-05-22 16:59 ` Liang, Kan
2017-05-22 16:55 ` Liang, Kan
2017-05-22 19:23 ` Peter Zijlstra
2017-05-22 19:28 ` Stephane Eranian
2017-05-22 21:51 ` Liang, Kan
2017-05-23 6:39 ` Peter Zijlstra
2017-05-23 6:42 ` Stephane Eranian
2017-05-24 15:45 ` Andi Kleen
2017-05-24 16:01 ` Vince Weaver
2017-05-24 16:55 ` Andi Kleen
2017-05-28 20:31 ` Stephane Eranian
2017-05-30 9:25 ` Peter Zijlstra
2017-05-30 13:51 ` Andi Kleen
2017-05-30 16:28 ` Peter Zijlstra
2017-05-30 16:41 ` Stephane Eranian
2017-05-30 17:22 ` Andi Kleen
2017-05-30 17:40 ` Peter Zijlstra
2017-05-30 17:51 ` Andi Kleen
2017-05-30 18:59 ` Peter Zijlstra
2017-05-30 19:40 ` Andi Kleen
2017-05-30 16:39 ` Stephane Eranian
2017-05-30 16:55 ` Thomas Gleixner
2017-05-30 17:25 ` Peter Zijlstra
2017-05-31 20:57 ` Vince Weaver
2017-05-28 2:56 ` kbuild test robot
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