From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261267AbULHRL4 (ORCPT ); Wed, 8 Dec 2004 12:11:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261270AbULHRL4 (ORCPT ); Wed, 8 Dec 2004 12:11:56 -0500 Received: from e2.ny.us.ibm.com ([32.97.182.142]:27071 "EHLO e2.ny.us.ibm.com") by vger.kernel.org with ESMTP id S261267AbULHRLw (ORCPT ); Wed, 8 Dec 2004 12:11:52 -0500 Date: Wed, 8 Dec 2004 09:05:04 -0800 From: Mike Kravetz To: Darren Hart Cc: lkml , blainey@ca.ibm.com, Martin J Bligh , nacc@us.ibm.com, johnstul@us.ibm.com, fultonm@ca.ibm.com, paulmck@us.ibm.com Subject: Re: nanosleep resolution, jiffies vs microseconds Message-ID: <20041208170504.GA4192@w-mikek2.beaverton.ibm.com> References: <1102524468.16986.30.camel@farah.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1102524468.16986.30.camel@farah.beaverton.ibm.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 08, 2004 at 08:47:48AM -0800, Darren Hart wrote: > I am looking at trying to improve the latency of nanosleep for short > sleep times (~1ms). After reading Martin Schwidefsky's post for cputime > on s390 (Message-ID: > <20041111171439.GA4900@mschwid3.boeblingen.de.ibm.com>), it seems to me > that we may be able to accomplish this by storing the expire time in > microseconds rather than jiffies. My only question would be 'why'? Is there some environment where this is an issue? -OR- Is this just 'something to do'? Seems to me that the only environment where this could be an issue is for 'realtime' tasks. For non-realtime, I would guess that the variability of preemption/scheduling makes this almost a non-issue. In environments where I have seen heavy use of nanosleep, there were other scheduling issues that almost always cause one to 'sleep' longer than the specified time. I'm not opposed to work in this area. Just curious as to why? -- Mike