From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268305AbUH2VPH (ORCPT ); Sun, 29 Aug 2004 17:15:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268314AbUH2VPH (ORCPT ); Sun, 29 Aug 2004 17:15:07 -0400 Received: from peabody.ximian.com ([130.57.169.10]:60588 "EHLO peabody.ximian.com") by vger.kernel.org with ESMTP id S268305AbUH2VPC (ORCPT ); Sun, 29 Aug 2004 17:15:02 -0400 Subject: Re: interrupt cpu time accounting? From: Robert Love To: Jeff Garzik Cc: Linux Kernel , Ingo Molnar In-Reply-To: <41323FA8.80203@pobox.com> References: <41323FA8.80203@pobox.com> Content-Type: text/plain Date: Sun, 29 Aug 2004 17:15:02 -0400 Message-Id: <1093814102.2595.8.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 1.5.93 (1.5.93-2) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2004-08-29 at 16:42 -0400, Jeff Garzik wrote: > Does the kernel scheduler notice when a CPU spends a lot of time doing > interrupt processing? > > For many network configurations you get the best cache affinity, etc. if > you lock network interrupts to a single CPU. However, on a box with > high network load, that could mean that that CPU is spending more time > processing interrupts than doing Real Work(tm). > > Will the scheduler "notice" this, and increasingly schedule processes > away from the interrupt-heavy CPU? Nope, not explicitly anyhow. Implicitly, at least, the load balancer will ensure that the runnable processes on the processor do not get "backed up" due to the delayed processing but you will still have the balanced minimum number of processes there. I don't know whether the answer is to use cpu affinity and not schedule processes on that processor when you bind interrupts to it, or an automatic algorithm in the load balance for doing it, but that is a neat idea. Robert Love