linux-kernel - Re: "perf: interrupt took too long" messages even with perf_cpu_time_max

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Date:	Wed, 13 Apr 2016 12:03:27 +0200
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: Re: "perf: interrupt took too long" messages even with
 perf_cpu_time_max_percent==0

On 2016.04.02 at 13:00 +0200, Peter Zijlstra wrote:
> On Sat, Apr 02, 2016 at 11:32:39AM +0200, Markus Trippelsdorf wrote:
> > Current git kernel sometimes shows:
> > 
> >  perf: interrupt took too long (71 > 52), lowering kernel.perf_event_max_sample_rate to 300
> >  perf: interrupt took too long (103 > 88), lowering kernel.perf_event_max_sample_rate to 300
> >  perf: interrupt took too long (130 > 128), lowering kernel.perf_event_max_sample_rate to 300
> >  perf: interrupt took too long (175 > 162), lowering kernel.perf_event_max_sample_rate to 300
> >  perf: interrupt took too long (219 > 218), lowering kernel.perf_event_max_sample_rate to 300
> > ...
> > 
> > when running e.g. "perf top" even when  
> > /proc/sys/kernel/perf_cpu_time_max_percent is set to 0.
> 
> 
> Ah, was 0 also meant to disable it?
> 
> Does the below help?

Yes, it obviously fixes the issue.

-- 
Markus