Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 3 Sep 2002 12:41:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 3 Sep 2002 12:41:56 -0400 Received: from otter.mbay.net ([206.55.237.2]:40204 "EHLO otter.mbay.net") by vger.kernel.org with ESMTP id convert rfc822-to-8bit; Tue, 3 Sep 2002 12:41:55 -0400 From: John Alvord To: Ingo Molnar Cc: Tobias Ringstrom , Alan Cox , Kernel Mailing List Subject: Re: Problem with the O(1) scheduler in 2.4.19 Date: Tue, 03 Sep 2002 09:46:09 -0700 Message-ID: References:

In-Reply-To: X-Mailer: Forte Agent 1.92/32.570 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1988 Lines: 44 On Tue, 3 Sep 2002 12:28:18 +0200 (CEST), Ingo Molnar wrote: > >On Tue, 3 Sep 2002, Tobias Ringstrom wrote: > >> For the case of a game server, this means that when the CPU utilization >> gets above 50% (roughly), it will switch from -5 to +5 in dynamic >> priority in a few seconds and stay there until the CPU utilization drops >> under 50%. >> >> Is my analysis correct, and is this what we want? > >do you expect a task that uses up 50% CPU time over an extended period of >time to be rated 'interactive'? > >we might make the '50%' rule to be '100% / nr_running_avg', so that if >your task is the only one in the system then it gets rated interactive - >but i suspect it will still be rated a CPU hog if it keeps trying to use >up 50% of CPU time even during busier periods. I have tried the >(1/nr_running) rule in earlier incarnations of the scheduler, and it didnt >make much difference, but we obviously need a boundary case like yours to >see the differences. > >> I tried that yesterday (without the O(1) scheduler), and it does wonders >> for the in-game latency (i.e. ping). I suppose that the dynamic prio >> will still be +5 at 70% CPU utilization even with a HZ of 1000 using the >> O(1) scheduler. Why would it make a difference? > >(it could in theory make a difference in some rare cases, in which the >frequency of sampling resonates with internal timings of the application - >i asked for this only to make sure there are no interactions.) > It seems to me that this condition could arise for any server process which is used by many interactive processes. Imagine 300 users and a server process which needs 70% to do the work. This could be a database server as well as the current game server. john - 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/