From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966936AbcAZRJD (ORCPT ); Tue, 26 Jan 2016 12:09:03 -0500 Received: from mail-wm0-f42.google.com ([74.125.82.42]:36073 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965088AbcAZRI7 (ORCPT ); Tue, 26 Jan 2016 12:08:59 -0500 Message-ID: <1453828136.3534.9.camel@gmail.com> Subject: Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable again and shut down on idle) From: Mike Galbraith To: Christoph Lameter Cc: Michal Hocko , Peter Zijlstra , LKML Date: Tue, 26 Jan 2016 18:08:56 +0100 In-Reply-To: References: <20160121082402.GA29520@dhcp22.suse.cz> <20160121165148.GF29520@dhcp22.suse.cz> <20160122140418.GB19465@dhcp22.suse.cz> <20160122161201.GC19465@dhcp22.suse.cz> <1453566115.3529.8.camel@gmail.com> <20160125174224.GH23934@dhcp22.suse.cz> <1453774465.3642.13.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2016-01-26 at 10:26 -0600, Christoph Lameter wrote: > On Tue, 26 Jan 2016, Mike Galbraith wrote: > > > > Why would the deferring cause this overhead? > > > > Because we schedule to idle cores aggressively, thus we may pop in and > > out of idle at high frequency. > > Whats the point of going idle if you have things to do soon? When a task schedules off, how do you know it'll be back at all, much less soon? -Mike