From: Andi Kleen <ak@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>,
Vince Weaver <vincent.weaver@maine.edu>,
"Liang, Kan" <kan.liang@intel.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"alexander.shishkin@linux.intel.com"
<alexander.shishkin@linux.intel.com>,
"acme@redhat.com" <acme@redhat.com>,
"jolsa@redhat.com" <jolsa@redhat.com>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"tglx@linutronix.de" <tglx@linutronix.de>
Subject: Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter
Date: Tue, 30 May 2017 10:22:08 -0700 [thread overview]
Message-ID: <20170530172208.GL24144@tassilo.jf.intel.com> (raw)
In-Reply-To: <20170530162838.h5tzdnrxpy6upbka@hirez.programming.kicks-ass.net>
> > You would only need a single one per system however, not one per CPU.
> > RCU already tracks all the CPUs, all we need is a single NMI watchdog
> > that makes sure RCU itself does not get stuck.
> >
> > So we just have to find a single watchdog somewhere that can trigger
> > NMI.
>
> But then you have to IPI broadcast the NMI, which is less than ideal.
Only when the watchdog times out to print the backtraces.
>
> RCU doesn't have that problem because the quiescent state is a global
> thing. CPU progress, which is what the NMI watchdog tests, is very much
> per logical CPU though.
RCU already has a CPU stall detector. It should work (and usually
triggers before the NMI watchdog in my experience unless the
whole system is dead)
-Andi
next prev parent reply other threads:[~2017-05-30 17:22 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
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 [this message]
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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