From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751991Ab3B1Hmb (ORCPT ); Thu, 28 Feb 2013 02:42:31 -0500 Received: from e28smtp09.in.ibm.com ([122.248.162.9]:37997 "EHLO e28smtp09.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751315Ab3B1Hma (ORCPT ); Thu, 28 Feb 2013 02:42:30 -0500 Message-ID: <512F0A5C.8030405@linux.vnet.ibm.com> Date: Thu, 28 Feb 2013 15:42:20 +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> <512F09D4.1020307@linux.vnet.ibm.com> In-Reply-To: <512F09D4.1020307@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13022807-2674-0000-0000-000007FDF218 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/28/2013 03:40 PM, Michael Wang wrote: > 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? I mean could we say that more ops/sec means more works has been done? Regards, Michael Wang > > 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/ >> >