From owner-freebsd-stable@FreeBSD.ORG Thu Dec 15 09:44:25 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 0BD63106566B for ; Thu, 15 Dec 2011 09:44:25 +0000 (UTC) (envelope-from tevans.uk@googlemail.com) Received: from mail-vw0-f54.google.com (mail-vw0-f54.google.com [209.85.212.54]) by mx1.freebsd.org (Postfix) with ESMTP id B4AAB8FC19 for ; Thu, 15 Dec 2011 09:44:24 +0000 (UTC) Received: by vbbfr13 with SMTP id fr13so2220200vbb.13 for ; Thu, 15 Dec 2011 01:44:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=mmPHE2NiEq+cRe+tfaqPX0Z8/KCa95i+Hmpas6bJ8R0=; b=iHzD8x8/iArXv4G7kdangK6W3FaWgtPRuu42cmfSnVDHzy6pcbhlEodFKrThc8NUjy 1R0d6WsJzXrRfQHtGq4TDebU44w75X70O8LJHCVBfbhHnjYjhHHGjveTLgk3lgapII9p u3Q+Lg0hJoLQIE3D43fs4Hae7DP9+b55Ylt7U= MIME-Version: 1.0 Received: by 10.52.23.2 with SMTP id i2mr1854149vdf.126.1323942264058; Thu, 15 Dec 2011 01:44:24 -0800 (PST) Received: by 10.52.162.202 with HTTP; Thu, 15 Dec 2011 01:44:23 -0800 (PST) In-Reply-To: <20111215004205.GA11556@icarus.home.lan> References: <4EE1EAFE.3070408@m5p.com> <4EE2AE64.9060802@m5p.com> <4EE88343.2050302@m5p.com> <4EE933C6.4020209@zedat.fu-berlin.de> <20111215004205.GA11556@icarus.home.lan> Date: Thu, 15 Dec 2011 09:44:23 +0000 Message-ID: From: Tom Evans To: Jeremy Chadwick Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: freebsd-stable@freebsd.org Subject: Re: SCHED_ULE should not be the default X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Dec 2011 09:44:25 -0000 On Thu, Dec 15, 2011 at 12:42 AM, Jeremy Chadwick wrote: > On Thu, Dec 15, 2011 at 12:39:50AM +0100, O. Hartmann wrote: >> On 12/14/11 18:54, Tom Evans wrote: >> > I believe the correct thing to do is to put some extra documentation >> > into the handbook about scheduler choice, noting the potential issues >> > with loading NCPU+1 CPU bound processes. Perhaps making it easier to >> > switch scheduler would also help? > > Replying to Tom's comment here: > > It is already easy to switch schedulers. =C2=A0You change the option in y= our > kernel config, rebuild kernel (world isn't necessary as long as you > haven't csup'd between your last rebuild and now), make installkernel, > shutdown -r now, done. Your definition of 'easy' differs wildly from mine. How is that in any way 'easy' to do across 200 servers? > > If what you're proposing is to make the scheduler changeable in > real-time? =C2=A0I think that would require a **lot** of work for somethi= ng > that very few people would benefit from (please stop for a moment and > think about the majority of the userbase, not just niche environments; I > say this politely, not with any condescension BTW). =C2=A0Sure, it'd be > "nice to have", but should be extremely low on the priority list (IMO). Real time scheduler changing would be insane! I was thinking that both/any/all schedulers could be compiled into the kernel, and the choice of which one to use becomes a boot time configuration. You don't have to recompile the kernel to change timecounter. Cheers Tom