From owner-freebsd-stable@FreeBSD.ORG Mon Nov 8 21:11:06 2004 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 033A516A4CE; Mon, 8 Nov 2004 21:11:06 +0000 (GMT) Received: from mail.vicor-nb.com (bigwoop.vicor-nb.com [208.206.78.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id AFB1943D53; Mon, 8 Nov 2004 21:11:05 +0000 (GMT) (envelope-from julian@elischer.org) Received: from elischer.org (julian.vicor-nb.com [208.206.78.97]) by mail.vicor-nb.com (Postfix) with ESMTP id 68FED7A445; Mon, 8 Nov 2004 13:11:05 -0800 (PST) Message-ID: <418FE0E8.1020702@elischer.org> Date: Mon, 08 Nov 2004 13:11:04 -0800 From: Julian Elischer User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.3.1) Gecko/20030516 X-Accept-Language: en, hu MIME-Version: 1.0 To: Robert Watson References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit cc: freebsd-stable@freebsd.org cc: jhb@freebsd.org cc: Emanuel Strobl cc: ups@freebsd.org cc: Mipam cc: julian@freebsd.org Subject: Re: preemption stable under 5.3? X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Nov 2004 21:11:06 -0000 Robert Watson wrote: >On Mon, 8 Nov 2004, Mipam wrote: > > > >>Thanks for your reply, okay, then i'd like to enable preemption. I >>noticed it's not in the GENERIC kernel config file. So: options >>PREEMPTION would suffice to enable it i guess? Any experience with >>preemption. noticable changes? So the problem: "PREEMPTION triggers >>frequent hangs" is resolved? Btw, is RELENG_5 also stable or only for >>early adopters? I really would like to see ule working stable in >>combination with preemption, but in 5.3 it won't happen. Maybe ule will >>be enabled later in the 5 series? >> >> > >There was a series of bugs in the scheduler which got tickled by >preemption; I'm unclear as to whether they were all resolved before 5.3 or >whether they require fixes in HEAD that haven't yet been merged. It may >well be safe, but I make no promises. Hopefully we can trick Julian or >John into responding to this thread. :-) Having it off by default on 5.3 >is certainly the more conservative (and reasonable) position, but if it >helps your environment and appears stable, there should be no reason not >to turn it on. It should substantially improve latency in interrupt >processing as well as packet processing. > I think that PREEMPTION with SCHED_4BSD might be ok.. It's hard to say because it's always harder to prove something correct than to prove it broken :-) Hopefully with the rush off, we can sit down and try "prove it ok" and take some cleanup passes over it. I still owe my wife a significant "chunk-o-time" (TM) however so count me out for a while . Hopefully however ups@ is coming online again this week.