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 12:40:17 -0700 [thread overview]
Message-ID: <20170530194017.GN24144@tassilo.jf.intel.com> (raw)
In-Reply-To: <20170530185957.jxl5tfnqfyjot75x@hirez.programming.kicks-ass.net>
> > BTW there's an alternative solution in cycling the NMI watchdog over
> > all available CPUs. Then it would eventually cover all. But that's
> > less real time friendly than relying on RCU.
>
> I don't think we need to worry too much about the watchdog being rt
> friendly. Robustness is the thing that worries me most.
Ok. Then just cycling is the most robust method, and it's very
simple.
You're right. Perhaps it's better than to rely on the RCU machinery which
seems to become ever more and more complex.
People who care extremely about latencies can just turn it off.
The main problem with the proposal is that it depends on the BIOS not
locking the TCO watchdog. On the systems were it is locked we would
either need to continue using the PMU for the watchdog, or find some other
watchdog source that can be programmed to be a NMI.
-Andi
next prev parent reply other threads:[~2017-05-30 19:40 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
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 [this message]
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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