From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753556AbZKWOJG (ORCPT ); Mon, 23 Nov 2009 09:09:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753080AbZKWOJF (ORCPT ); Mon, 23 Nov 2009 09:09:05 -0500 Received: from casper.infradead.org ([85.118.1.10]:47391 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753000AbZKWOJE (ORCPT ); Mon, 23 Nov 2009 09:09:04 -0500 Subject: Re: LinSched updated to current linux kernel version From: Peter Zijlstra To: Jon Tore Hafstad Cc: linux-kernel@vger.kernel.org, dhaval.giani@gmail.com, mingo@elte.hu, tglx@linutronix.de, bbb@cs.unc.edu, henrik@austad.us, jmc@cs.unc.edu, Jeff Dike In-Reply-To: <78b8ce680911181211k6c15a976u52186b5849224040@mail.gmail.com> References: <78b8ce680911181211k6c15a976u52186b5849224040@mail.gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 23 Nov 2009 15:08:15 +0100 Message-ID: <1258985295.4531.496.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2009-11-18 at 21:11 +0100, Jon Tore Hafstad wrote: > Hi all > > I wish to inform you about an update of LinSched (The Linux Scheduler > Simulator([1])) I'm currently working on. > == Motivation == > I wished to implement different EDF schedulers to gain a better > understanding of kernel internals as well as scheduling dynamics. I > got some feedback from Henrik Austad that LinSched was a tool that > made implementing a scheduler in to the linux kernel easier, since > the code compiles in a fraction of the time the kernel does (Yes, I > know you can pull all sorts of tricks and tweaks in order to speed up > a kernel compilation), a segfault will be a segfault, and not a kernel > oops ;),and the full range of debuggers and memory analyzers will be > available. I would have expected people to use UML for this (User-Mode-Linux, not the draw lots of silly pictures thing). The main draw-back is that UML doesn't currently support SMP and any interesting preemption modes, but adding that to UML would help out more people -- I know the VM (virtual Memory, not the machine thing) people used to use UML for exactly these reasons, easy gdb, etc.. But I suspect that with KVM's gdb stub getting usable more and more people are abandoning this. > == Remaining Work == > One of the major issues right now is the hrtimers, which large > portions of the scheduler now use. I have not decided exactly how to > solve this issue yet,but this will be the focus of my work for the > coming weeks. The typical implementation would be signals using the posix timers. Have the spin_lock_irq variants mask signals etc..