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

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Date:	Sat, 2 Apr 2016 11:32:39 +0200
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	linux-kernel@...r.kernel.org
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: "perf: interrupt took too long" messages even with
 perf_cpu_time_max_percent==0

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.

-- 
Markus