From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932075AbaHFS7H (ORCPT ); Wed, 6 Aug 2014 14:59:07 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:56265 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1756284AbaHFS7E (ORCPT ); Wed, 6 Aug 2014 14:59:04 -0400 From: "Rafael J. Wysocki" To: Mel Gorman Cc: Rafael J Wysocki , Nicolas Pitre , Mike Galbraith , LKML Subject: Re: [PATCH 0/4] Reduce overhead of menu governor Date: Wed, 06 Aug 2014 21:17:45 +0200 Message-ID: <3495244.HqlX2f8Ijd@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.16.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1407331161-4642-1-git-send-email-mgorman@suse.de> References: <1407331161-4642-1-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, August 06, 2014 02:19:17 PM Mel Gorman wrote: > The menu_select function is heavy and is very noticable in profiles for > workloads that enter/leave idle state a lot. This primarily happens > for scheduler microbenchmarks. The biggest contibution is the standard > deviation calculations and comparisons but the excessive calls into > the scheduler core do not help. > > It would be nice to reduce the number of times nr_iowait is checked to > once per 8 intervals but I was not sure how to measure what the general > impact of such a change could be. > > Similiarly I looked at different ways the standard deviation could be > calculated but the standard equivalent calculations potentially overflow. > It could be done as rolling average and rolling deviation but again > it was unclear how that could be evaluated. Tips on how the goodness/badness > of governor changes are evalated would be nice. > > In the meantime, here are patches against some of the obvious stuff. They look good, I'm going to apply them. Rafael