From owner-freebsd-current@FreeBSD.ORG Thu Jan 3 05:52:45 2013 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id E965A71D; Thu, 3 Jan 2013 05:52:45 +0000 (UTC) (envelope-from kob6558@gmail.com) Received: from mail-ea0-f176.google.com (mail-ea0-f176.google.com [209.85.215.176]) by mx1.freebsd.org (Postfix) with ESMTP id E335C6CE; Thu, 3 Jan 2013 05:52:44 +0000 (UTC) Received: by mail-ea0-f176.google.com with SMTP id d13so5967972eaa.7 for ; Wed, 02 Jan 2013 21:52:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=YIee0nzPlls5BnzFjKLFHW7KoULSislsRykqse+eXTw=; b=PhzqX8ilrQY+1U+fo3LmWn5BIEhr+UvMkrclm3V7ctg08p26oOrMSmLRsy7YofqmGN U75qKZv4DoBeDgOiVn91Jk71GnGNOlDVo+/7Xs07TiPgs/KdKMxin+m8JUOkbkL+yZvA 33OnhVMRQwIRxc/mRBlwEM2ZI8eCr0NcIEb8kZNeiCM6RzosYQDY5G/qknV9iv4EHjz9 jTofSwPkY8GOX/Oq9i/9fznwptIZ1BNRGpMXu7uV9gU79nvYg2ZCW7rDyB24p5/tVpY/ +E9R8WjEUDbVAI7RpCJ3fofcO6NinxswQJPmk5EIfF+MUHBeXy2PCSLkbpmbY8xUH2RI Hg0g== MIME-Version: 1.0 Received: by 10.14.184.134 with SMTP id s6mr130647516eem.43.1357192358178; Wed, 02 Jan 2013 21:52:38 -0800 (PST) Received: by 10.223.170.193 with HTTP; Wed, 2 Jan 2013 21:52:37 -0800 (PST) In-Reply-To: <50E4AF4C.2070902@FreeBSD.org> References: <50CCAB99.4040308@FreeBSD.org> <50CE5B54.3050905@FreeBSD.org> <50D03173.9080904@FreeBSD.org> <20121225232126.GA47692@alchemy.franken.de> <50DB4EFE.2020600@FreeBSD.org> <1356909223.54953.74.camel@revolution.hippie.lan> <20121231061735.GA5866@onelab2.iet.unipi.it> <50E16637.9070501@FreeBSD.org> <20130102105730.GA42542@onelab2.iet.unipi.it> <50E418EA.7030801@FreeBSD.org> <20130102122743.GA43241@onelab2.iet.unipi.it> <1357135374.54953.150.camel@revolution.hippie.lan> <50E4AF4C.2070902@FreeBSD.org> Date: Wed, 2 Jan 2013 21:52:37 -0800 Message-ID: Subject: Re: [RFC/RFT] calloutng From: Kevin Oberman To: Alexander Motin Content-Type: text/plain; charset=UTF-8 Cc: Davide Italiano , Ian Lepore , Adrian Chadd , Marius Strobl , FreeBSD Current , freebsd-arch@freebsd.org, Luigi Rizzo X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 03 Jan 2013 05:52:46 -0000 On Wed, Jan 2, 2013 at 2:06 PM, Alexander Motin wrote: > On 02.01.2013 18:08, Adrian Chadd wrote: >> >> .. I'm pretty damned sure we're going to need to enforce a "never >> earlier than X" latency. > > > Do you mean here that we should never wake up before specified time (just as > specified by the most of existing APIs), or that we should not allow sleep > shorter then some value to avoid DoS? At least on x86 nanosleep(0) doesn't > allow to block the system. Also there is already present mechanism for > specifying minimum timer programming interval in eventtimers(9) KPI. I can see serious performance issues with some hardware (wireless comes to mind) if things happen too quickly. Intuition is that it could also play hob with VMs. I believe that the proper way is to wake between T_X and T_X + D. This assumes that D is max_wake_delay, not deviation, which leaves us at the original of (T_X) =< event_time =< (T_X + D). -- R. Kevin Oberman, Network Engineer E-mail: kob6558@gmail.com