From owner-freebsd-arch@FreeBSD.ORG Thu Mar 1 01:16:53 2012 Return-Path: Delivered-To: arch@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 576021065670 for ; Thu, 1 Mar 2012 01:16:53 +0000 (UTC) (envelope-from bakul@bitblocks.com) Received: from mail.bitblocks.com (ns1.bitblocks.com [173.228.5.8]) by mx1.freebsd.org (Postfix) with ESMTP id 3EC078FC16 for ; Thu, 1 Mar 2012 01:16:53 +0000 (UTC) Received: from bitblocks.com (localhost [127.0.0.1]) by mail.bitblocks.com (Postfix) with ESMTP id CB4AC1CC32; Wed, 29 Feb 2012 16:58:54 -0800 (PST) To: Bruce Evans In-reply-to: Your message of "Thu, 01 Mar 2012 11:33:46 +1100." <20120301071145.O879@besplex.bde.org> References: <20120229194042.GA10921@onelab2.iet.unipi.it> <20120301071145.O879@besplex.bde.org> Comments: In-reply-to Bruce Evans message dated "Thu, 01 Mar 2012 11:33:46 +1100." Date: Wed, 29 Feb 2012 16:58:54 -0800 From: Bakul Shah Message-Id: <20120301005854.CB4AC1CC32@mail.bitblocks.com> Cc: arch@FreeBSD.org Subject: Re: select/poll/usleep precision on FreeBSD vs Linux vs OSX X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Mar 2012 01:16:53 -0000 On Thu, 01 Mar 2012 11:33:46 +1100 Bruce Evans wrote: > Linux and OSX must be using busy-waiting or expensive timer > reprogramming for short timeouts to work. Linux-2.6.17 or later have two options: CONFIG_NO_HZ for on demand timer interrupts (to reduce power use on idle systems) and CONFIG_HIGH_RES_TIMERS for as accurate timers as h/w would allow. And yes, timers are reprogrammed (as per a June 23, 2006 kerneltrap.org article).