Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752565Ab3HUQsK (ORCPT ); Wed, 21 Aug 2013 12:48:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5297 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751633Ab3HUQsJ (ORCPT ); Wed, 21 Aug 2013 12:48:09 -0400 Date: Wed, 21 Aug 2013 18:41:46 +0200 From: Oleg Nesterov To: Peter Zijlstra Cc: Arjan van de Ven , Fernando Luis =?iso-8859-1?Q?V=E1zquez?= Cao , Frederic Weisbecker , Ingo Molnar , Thomas Gleixner , LKML , Tetsuo Handa , Andrew Morton Subject: Re: [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock Message-ID: <20130821164146.GA15194@redhat.com> References: <20130820084405.GC3258@twins.programming.kicks-ass.net> <52138BE9.5090005@linux.intel.com> <20130820160146.GG3258@twins.programming.kicks-ass.net> <20130820163312.GA17957@redhat.com> <20130820175429.GI3258@twins.programming.kicks-ass.net> <20130820182553.GB22287@redhat.com> <20130821083130.GM3258@twins.programming.kicks-ass.net> <20130821113551.GA1472@redhat.com> <20130821123311.GA31370@twins.programming.kicks-ass.net> <20130821142356.GC31370@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130821142356.GC31370@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 980 Lines: 25 On 08/21, Peter Zijlstra wrote: > > The other consideration is that this adds two branches to the normal > schedule path. I really don't know what the regular ratio between > schedule() and io_schedule() is -- and I suspect it can very much depend > on workload -- but it might be a net loss due to that, even if it makes > io_schedule() 'lots' cheaper. Yes, agreed. Please ignore it for now, I didn't try to actually suggest this change. And even if this is fine perfomance wise, this needs some benchmarking. Well. actually I have a vague feeling that _perhaps_ this change can help to solve other problems we are discussing, but I am not sure and right now I can't even explain the idea to me. In short: please ignore ;) Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/