From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752191Ab3B1HkU (ORCPT ); Thu, 28 Feb 2013 02:40:20 -0500 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:35807 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750775Ab3B1HkP (ORCPT ); Thu, 28 Feb 2013 02:40:15 -0500 Message-ID: <512F09D4.1020307@linux.vnet.ibm.com> Date: Thu, 28 Feb 2013 15:40:04 +0800 From: Michael Wang User-Agent: Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 To: Mike Galbraith CC: LKML , Ingo Molnar , Peter Zijlstra , Paul Turner , Alex Shi , Andrew Morton , Ram Pai , "Nikunj A. Dadhania" , Namhyung Kim Subject: Re: [RFC PATCH] sched: wakeup buddy References: <512EFB4B.5040204@linux.vnet.ibm.com> <1362035917.4460.105.camel@marge.simpson.net> In-Reply-To: <1362035917.4460.105.camel@marge.simpson.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13022807-9574-0000-0000-000006C87B90 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Mike Thanks for your reply. On 02/28/2013 03:18 PM, Mike Galbraith wrote: > On Thu, 2013-02-28 at 14:38 +0800, Michael Wang wrote: > >> + /* >> + * current is the only task on rq and it is >> + * going to sleep, current cpu will be a nice >> + * candidate for p to run on. >> + */ > > The sync hint only means it might be going to sleep soon, and even then, > there can still be enough execution overlap to be a win to schedule > cross core. Sched pipe numbers will always be much prettier if you do > wakeup cpu affine, as it's ~100% scheduler and ~100% sync. Hmm.. so it's the comparison between 'cache benefit - execution overlap' and 'latency - execution overlap'? I could not estimate how many latency will be added to wait for current going to sleep (it should be faster than access cold data, isn't it?), but I really like the cache benefit, unless sync doesn't means current is going to sleep every time, but that's the promise of WF_SYNC, isn't it? You may lose > a lot on other stuff if you interpret the hint as gospel truth. Could you please give more details on this point? > > IMHO, sched pipe is a "how fat have I become" benchmark, not "how well > do I perform". The scheduler performs well when it makes more work > happen. Playing ping-pong with yourself is _exercise_, not a job :) That's right, may be I'm using the wrong description, it's the ops/sec which has been doubled, that means 'fat', correct? Regards, Michael Wang > > -Mike > > -- > 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/ >