From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 6 Jan 2001 21:48:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 6 Jan 2001 21:47:59 -0500 Received: from isis.its.uow.edu.au ([130.130.68.21]:5573 "EHLO isis.its.uow.edu.au") by vger.kernel.org with ESMTP id ; Sat, 6 Jan 2001 21:47:47 -0500 Message-ID: <3A57DA3E.6AB70887@uow.edu.au> Date: Sun, 07 Jan 2001 13:53:50 +1100 From: Andrew Morton X-Mailer: Mozilla 4.7 [en] (X11; I; Linux 2.4.0-test8 i586) X-Accept-Language: en MIME-Version: 1.0 To: lkml , lad Subject: low-latency scheduling patch for 2.4.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org A patch against kernel 2.4.0 final which provides low-latency scheduling is at http://www.uow.edu.au/~andrewm/linux/schedlat.html#downloads Some notes: - Worst-case scheduling latency with *very* intense workloads is now 0.8 milliseconds on a 500MHz uniprocessor. For normal workloads you can expect to achieve better than 0.5 milliseconds for ever. For example, worst-case latency between entry to an interrupt routine and activation of a usermode process during a `make clean && make bzImage' is 0.35 milliseconds. This is one to three orders of magnitude better than BeOS, MacOS and the Windowses. - Low latency is enabled from the `Processor type and features' kernel configuration menu for all architectures. It would be nice to hear from non-x86 users. - The SMP problem hasn't been addressed. Enabling low-latency for SMP works well under normal workloads but comes unstuck under very heavy workloads. I'll be taking a further look at this. - The supporting tools `rtc_debug' and `amlat' have been updated. These are quite useful tools for providing accurate measurement of latencies. They may also be used to identify the causes of poor latency in the kernel. - Remaining problem areas (the Don't Do That list) is pretty small: - Scrolling the fb console. - Running hdparm. - Using LILO - Starting the X server - Low latency will probably only be achieved when using the ext2 and NFS filesystems. - If you care about latency, be *very* cautious about upgrading to XFree86 4.x. I'll cover this issue in a separate email, copied to the XFree team. - - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/