From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arjan van de Ven Subject: Re: multiqueue interrupts... Date: Fri, 19 Sep 2008 15:11:20 -0700 Message-ID: <20080919151120.6f397192@infradead.org> References: <20080918.193815.175549834.davem@davemloft.net> <41b516cb0809191050t6c9783dele8926f697854bb1@mail.gmail.com> <20080919181840.GE30956@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: David Miller , netdev@vger.kernel.org To: Matthew Wilcox Return-path: Received: from casper.infradead.org ([85.118.1.10]:58052 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752082AbYISWLW (ORCPT ); Fri, 19 Sep 2008 18:11:22 -0400 In-Reply-To: <20080919181840.GE30956@parisc-linux.org> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 19 Sep 2008 12:18:41 -0600 Matthew Wilcox wrote: > > Another idea I've been thinking about is a flag to tell irqbalance to > leave stuff alone, and we just set stuff up right the first time. that's not a good answer. There are reasons for moving interrupts that are a sysadmin choice (like power management policy that if the system is seriously idle, that all interrupts go to one of the sockets so that the others can stay in low power mode). Putting the policy in the kernel to prohibit such admin choices sounds like a bad idea to me. There are better ways to do what you want, for example by exposing a "preferred cpu" somewhere so that irqbalance will place it there "unless <...>". That is, if such kernel policy binding is right in the first place > In a storage / NUMA configuration we really want to set up one queue > per cpu / package / node (depending on resource constraints) and know > that the interrupt is going to come back to the same cpu / package / > node. We definitely don't want irqbalanced moving the interrupt > around. irqbalance is NUMA aware and places a penalty on placing an interrupt "wrongly". We can argue on how strong this penalty should be, but thinking that irqbalance doesn't use the numa info the kernel exposes is incorrect. -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org