From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263760AbTJ0XPy (ORCPT ); Mon, 27 Oct 2003 18:15:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263762AbTJ0XPy (ORCPT ); Mon, 27 Oct 2003 18:15:54 -0500 Received: from mail-10.iinet.net.au ([203.59.3.42]:42903 "HELO mail.iinet.net.au") by vger.kernel.org with SMTP id S263760AbTJ0XPv (ORCPT ); Mon, 27 Oct 2003 18:15:51 -0500 Message-ID: <3F9DA68F.5080000@cyberone.com.au> Date: Tue, 28 Oct 2003 10:13:19 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030827 Debian/1.4-3 X-Accept-Language: en MIME-Version: 1.0 To: Andrew Theurer CC: linux-kernel Subject: Re: Nick's scheduler v17 References: <3F996B10.4080307@cyberone.com.au> <3F99CE07.6030905@cyberone.com.au> <3F9B6D24.7050003@cyberone.com.au> <200310271102.59041.habanero@us.ibm.com> In-Reply-To: <200310271102.59041.habanero@us.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Theurer wrote: >>>> *imbalance = min(this_load - load_avg, load_avg - max_load) >>>> >>>>That way you take just enough to either have busiest_queue or >>>>this_rq's length be the load_avg. I suppose you could take even >>>>less, but IMO, the /=2 is what I really don't like. Perhaps: >>>> >>>That is _exactly_ what I had before! Thats probably the way to go. Thanks >>>for having a look at it. >>> >>> >>>>*imbalance = min(this_load - load_avg, load_avg - max_load); >>>>*imbalance = (*imbalance + FPT - 1) / FPT; >>>> >>>>This should work well for intranode balances, internode balances may >>>>need a little optimization, since the load_avg really does not really >>>>represent the load avg of the two nodes in question, just one cpu >>>>from one of them and all the cpus from another. >>>> >>Oh, actually, after my path, load_avg represents the load average of _all_ >>the nodes. Have a look at find_busiest_node. Which jogs my memory of why >>its not always a good idea to do your *imbalance min(...) thing (I actually >>saw this happening). >> > >Oops, I meant avg_load, which you calculate in find_busiest_queue on the fly. > OK > >>5 CPUs, 4 processes running on one cpu. load_avg would be 0.8 for all cpus. >>balancing doesn't happen. I have to think about this a bit more... >> > >Actually, if we use avg_load, I guess it would be 0, since this is an unsigned >long. Maybe avg_load needs to have a min value of 1. Then if we apply: > Well its got a fixed point scaling factor. > >*imbalance = min(max_load - avg_load, avg_load - this_load) > min(4 - 1, 1 - 0) > > I think you want: *imbalance = min(max_load - avg_load, avg_load - this_load) if ( (*imbalance < 1*FPT) && (max_load - this_load) > 1*FPT ) *imbalance = 1*FPT; So if there is a total imbalance of more than 1 task, at least one will be moved. > >And imbalance looks a lot better. Only concern would be an idle cpu stealing >from another, leaving the other cpu idle. I guess a check could be put >there. > > pull_task won't pull a running task, so you get some protection there.