Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 10 Apr 2001 08:41:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 10 Apr 2001 08:41:08 -0400 Received: from iris.mc.com ([192.233.16.119]:19151 "EHLO mc.com") by vger.kernel.org with ESMTP id ; Tue, 10 Apr 2001 08:40:06 -0400 From: Mark Salisbury To: Alan Cox , ak@suse.de (Andi Kleen) Subject: Re: No 100 HZ timer ! Date: Tue, 10 Apr 2001 08:27:13 -0400 X-Mailer: KMail [version 1.0.29] Content-Type: text/plain; charset=US-ASCII Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), ak@suse.de (Andi Kleen), mbs@mc.com (Mark Salisbury), jdike@karaya.com (Jeff Dike), schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org In-Reply-To: In-Reply-To: MIME-Version: 1.0 Message-Id: <0104100832191C.01893@pc-eng24.mc.com> Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 10 Apr 2001, Alan Cox wrote: > > Does not sound very attractive all at all on non virtual machines (I see the point on > > UML/VM): > > making system entry/context switch/interrupts slower, making add_timer slower, just to > > process a few less timer interrupts. That's like robbing the fast paths for a slow path. > > Measure the number of clocks executing a timer interrupt. rdtsc is fast. Now > consider the fact that out of this you get KHz or better scheduling > resolution required for games and midi. I'd say it looks good. I agree > the accounting of user/system time needs care to avoid slowing down syscall > paths > > Alan the system I implemented this in went from 25 Millisecond resolution to 25-60 Nanosecond resolution (depending on the CPU underneath). that is a theoretical factor of 500,000 to 1,000,000 improvement in resolution for timed events, and the clock overhead after the change was about the same. (+-10% depending on underlying CPU) this is on a system that only had one clock tick per process quantum, as opposed to the 10 in linux. -- /*------------------------------------------------** ** Mark Salisbury | Mercury Computer Systems ** ** mbs@mc.com | System OS - Kernel Team ** **------------------------------------------------** ** I will be riding in the Multiple Sclerosis ** ** Great Mass Getaway, a 150 mile bike ride from ** ** Boston to Provincetown. Last year I raised ** ** over $1200. This year I would like to beat ** ** that. If you would like to contribute, ** ** please contact me. ** **------------------------------------------------*/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/