From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761050AbYHDHJS (ORCPT ); Mon, 4 Aug 2008 03:09:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757758AbYHDHJF (ORCPT ); Mon, 4 Aug 2008 03:09:05 -0400 Received: from bay0-omc3-s18.bay0.hotmail.com ([65.54.246.218]:23680 "EHLO bay0-omc3-s18.bay0.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757119AbYHDHJE (ORCPT ); Mon, 4 Aug 2008 03:09:04 -0400 X-Greylist: delayed 368 seconds by postgrey-1.27 at vger.kernel.org; Mon, 04 Aug 2008 03:09:04 EDT Message-ID: X-Originating-IP: [199.203.130.251] From: Kostya B To: Subject: __do_softirq and real-time execution context Date: Mon, 4 Aug 2008 07:02:53 +0000 Importance: Normal In-Reply-To: References: Content-Type: text/plain; charset="windows-1255" Content-Transfer-Encoding: 8bit MIME-Version: 1.0 X-OriginalArrivalTime: 04 Aug 2008 07:02:53.0813 (UTC) FILETIME=[1DA95A50:01C8F600] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Please consider the following: __do_softirq could be run from several checkpoints in kernel and even can employ userspace process context. For example, under heavy network traffic such process could be blocked for a relatively large period until ksoftirqd wakes up and takes control for Rx/Tx. In the case of regular userspace process the ksoftirqd solves the kernel/user trade-off problem pretty well. However, in the case of _real-time_ process, such behavior may yield severe outcomes. Real-time (e.g. NTPL FIFO thread) might require short responses and low latency. The proposal is that __do_softirq should not run its pending tasks in the context of RT process. Just check has_rt_policy() and immediately wake up ksoftirqd. Regards, - Kostya _________________________________________________________________ Invite your mail contacts to join your friends list with Windows Live Spaces. It's easy! http://spaces.live.com/spacesapi.aspx?wx_action=create&wx_url=/friends.aspx&mkt=en-us