Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750827AbVJSL6E (ORCPT ); Wed, 19 Oct 2005 07:58:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750832AbVJSL6E (ORCPT ); Wed, 19 Oct 2005 07:58:04 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:64472 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1750827AbVJSL6B (ORCPT ); Wed, 19 Oct 2005 07:58:01 -0400 Date: Wed, 19 Oct 2005 13:58:14 +0200 From: Ingo Molnar To: Roman Zippel Cc: Tim Bird , Andrew Morton , tglx@linutronix.de, george@mvista.com, linux-kernel@vger.kernel.org, johnstul@us.ibm.com, paulmck@us.ibm.com, hch@infradead.org, oleg@tv-sign.ru Subject: Re: [PATCH] ktimers subsystem 2.6.14-rc2-kt5 Message-ID: <20051019115814.GB1580@elte.hu> References: <4353F936.3090406@am.sony.com> <20051017201330.GB8590@elte.hu> <20051018084655.GA28933@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=disabled SpamAssassin version=3.0.4 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2341 Lines: 50 * Roman Zippel wrote: > > > > e.g. we dont want a watchdog from being > > > > overload-able via too many timeouts in the timer wheel ... > > > > > > Please explain. > > > > e.g. on busy networked servers (i.e. ones that do have a need for > > watchdogs) the timer wheel often includes large numbers of timeouts, > > 99.9% of which never expire. If they do expire en masse for whatever > > reason, then we can get into overload mode: a million timers might have > > to expire before we get to process the watchdog event and act upon it. > > This can delay the watchdog event significantly, which delay might (or > > might not) matter to the watchdog application. > > I already mentioned earlier that it's possible to reduce the timer > load by using a watchdog timer to filter most of these events, so that > you get into the interesting situation that most kernel timer actually > do expire and suddenly you easily can have more "timers" than > "timeouts". this sentence does not parse at all, for me. Here's the effort i did trying to decypher it: Firstly, you mention 'watchdog' without clarifying whether it's the examplary watchdog we were talking about above, or whether it's some other, new mechanism. The former makes no sense (what does the watchdog timer in a random driver have to do with the millions of network timers i was talking about, and how could it be used to filter anything?), the later you dont explain. Secondly, the above sentence is the first time in the ktimer discussion that you ever mentioned the word 'filter', and you never mentioned the word 'watchdog' outside of the example we were discussing, so i'm curious about the source of the above "I already mentioned earlier" statement. When earlier? Which email? Frankly, the whole paragraph reads as if from another planet, i see the words but the content seems totally out of context and makes no sense to me. So i cannot even agree or disagree with anything you said in that sentence, because the sentence simply does not parse. Please enlighten me! Ingo - 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/