From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756901AbcAYL0M (ORCPT ); Mon, 25 Jan 2016 06:26:12 -0500 Received: from casper.infradead.org ([85.118.1.10]:38959 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755506AbcAYL0J (ORCPT ); Mon, 25 Jan 2016 06:26:09 -0500 Date: Mon, 25 Jan 2016 12:26:06 +0100 From: Peter Zijlstra To: Mel Gorman Cc: Ingo Molnar , Matt Fleming , Mike Galbraith , LKML Subject: Re: [PATCH] sched: Make schedstats a runtime tunable that is disabled by default Message-ID: <20160125112606.GV6357@twins.programming.kicks-ass.net> References: <1453716331-21029-1-git-send-email-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1453716331-21029-1-git-send-email-mgorman@techsingularity.net> 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 On Mon, Jan 25, 2016 at 10:05:31AM +0000, Mel Gorman wrote: > schedstats is very useful during debugging and performance tuning but it > incurs overhead. As such, even though it can be disabled at build time, > it is often enabled as the information is useful. This patch adds a > kernel command-line and sysctl tunable to enable or disable schedstats on > demand. It is disabled by default as someone who knows they need it can > also learn to enable it when necessary. So the reason its often enabled in distro configs is (IIRC) that it enables trace_sched_stat_{wait,sleep,iowait,blocked}(). I've not looked at the details of this patch, but I suspect this patch would make these tracepoints available but non-functional unless you poke the magic button.