From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kok, Auke" Subject: Re: [PATCH] e1000: Use deferrable timer for watchdog Date: Wed, 19 Dec 2007 13:38:22 -0800 Message-ID: <47698F4E.40209@intel.com> References: <47696AC9.90204@intel.com> <82e4877d0712191139k4dbae463icf2a59c8c0104010@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Arjan van de Ven To: Parag Warudkar Return-path: Received: from mga02.intel.com ([134.134.136.20]:21603 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752658AbXLSVjA (ORCPT ); Wed, 19 Dec 2007 16:39:00 -0500 In-Reply-To: <82e4877d0712191139k4dbae463icf2a59c8c0104010@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Parag Warudkar wrote: > On 12/19/07, Kok, Auke wrote: > [snip] > >> I can't possibly see any benefit from this other than that you just add up to a >> whole second to the initialization cycle, which is bad. >> > Well, Ok but it can't be bad - I've been using this patch sometime and > haven't seen any problem at all and powertop shows it reduces the > wakeups-from-idle. > > But whatever - no big deal since it already uses round_jiffies(). why would this patch reduce wakeups even more than round_jiffies()? Does it make our ~2 second update interval not reliable? can you quantify "shows it reduces" ? Or timer only runs once every two seconds... maybe I just don't understand the effect of timer_set_deferrable() - we're already deferring it ourselves when we want to. If that is not working then I suggest that we fix that first instead of postponing the critical first run of the e1000 watchdog task. People in the datacenter really don't want to see more delays when bringing up link, and we get frequent calls about it already being long on gigabit (not even minding spanning tree). Adding 25% to that time isn't going to down very nicely with them.