Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758036AbYH2SgS (ORCPT ); Fri, 29 Aug 2008 14:36:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753653AbYH2SgE (ORCPT ); Fri, 29 Aug 2008 14:36:04 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:37367 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751344AbYH2SgD (ORCPT ); Fri, 29 Aug 2008 14:36:03 -0400 Date: Fri, 29 Aug 2008 19:18:37 +0100 From: Alan Cox To: Linus Torvalds Cc: Arjan van de Ven , linux-kernel@vger.kernel.org, mingo@elte.hu, tglx@tglx.de Subject: Re: [PATCH 4/5] select: make select() use schedule_hrtimeout() Message-ID: <20080829191837.3d2b3050@lxorguk.ukuu.org.uk> In-Reply-To: References: <20080829080549.6906b744@infradead.org> <20080829080809.0e42a323@infradead.org> <20080829171108.63e6dcd4@lxorguk.ukuu.org.uk> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.11; x86_64-redhat-linux-gnu) Organization: Red Hat UK Cyf., Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, Y Deyrnas Gyfunol. Cofrestrwyd yng Nghymru a Lloegr o'r rhif cofrestru 3798903 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1391 Lines: 36 > I do agree that we could do that too, but you miss one big issue: even if > we were to add an accuracy field inside the kernel, there is no such field > in the user interfaces. Most of the timers we want to aggregate with are kernel originated and those also need accuracy fields (tcp retransmit is fairly precision at high speed while tcp keepalive is 'yeah whatever' sort of urgency. At the point we are merging timers we want to consider user kernel and in a virtualised environment across all guest. > We just pass timevals (and sometimes timespecs) around, and no, they don't > have any way to specify accuracy. Agreed for userspace. > Yeah, we could use the high bits in the usec/nsec words, but then older > kernels would basically do random things, so that would be a horrible > interface. Gak.... no... > And the only reasonable way to do that is to just look at the range. You > can probably do something fairly trivial with Agreed except that I'd assume real time tasks implied high accuracy, otherwise one assumes they'd have not have been real time - and probably putting those constants into sysfs somewhere. Alan -- 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/