Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752755AbcDBLA2 (ORCPT ); Sat, 2 Apr 2016 07:00:28 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:33557 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbcDBLA0 (ORCPT ); Sat, 2 Apr 2016 07:00:26 -0400 Date: Sat, 2 Apr 2016 13:00:17 +0200 From: Peter Zijlstra To: Markus Trippelsdorf Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin Subject: Re: "perf: interrupt took too long" messages even with perf_cpu_time_max_percent==0 Message-ID: <20160402110017.GP3448@twins.programming.kicks-ass.net> References: <20160402093239.GA305@x4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160402093239.GA305@x4> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1417 Lines: 36 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? --- kernel/events/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 8c3b35f2a269..21ba024c9ed1 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -412,7 +412,8 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write, if (ret || !write) return ret; - if (sysctl_perf_cpu_time_max_percent == 100) { + if (sysctl_perf_cpu_time_max_percent == 100 || + sysctl_perf_cpu_time_max_percent == 0) { printk(KERN_WARNING "perf: Dynamic interrupt throttling disabled, can hang your system!\n"); WRITE_ONCE(perf_sample_allowed_ns, 0);