From owner-freebsd-hackers@FreeBSD.ORG Wed Jun 4 15:07:14 2014 Return-Path: Delivered-To: hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 6DB039B; Wed, 4 Jun 2014 15:07:14 +0000 (UTC) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [IPv6:2001:470:1f11:75::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 476F62CA5; Wed, 4 Jun 2014 15:07:14 +0000 (UTC) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id B266EB98F; Wed, 4 Jun 2014 11:07:12 -0400 (EDT) From: John Baldwin To: freebsd-hackers@freebsd.org Subject: Re: Permit init(8) use its own cpuset group. Date: Wed, 4 Jun 2014 11:06:11 -0400 User-Agent: KMail/1.13.5 (FreeBSD/8.4-CBSD-20140415; KDE/4.5.5; amd64; ; ) References: <538C8F9A.4020301@FreeBSD.org> <20140602164850.GS3991@kib.kiev.ua> In-Reply-To: <20140602164850.GS3991@kib.kiev.ua> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201406041106.11659.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Wed, 04 Jun 2014 11:07:12 -0400 (EDT) Cc: Konstantin Belousov , hackers@freebsd.org, "Alexander V. Chernikov" X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Jun 2014 15:07:14 -0000 On Monday, June 02, 2014 12:48:50 pm Konstantin Belousov wrote: > On Mon, Jun 02, 2014 at 06:52:10PM +0400, Alexander V. Chernikov wrote: > > Hello list! > > > > Currently init(8) uses group 1 which is root group. > > Modifications of this group affects both kernel and userland threads. > > Additionally, such modifications are impossible, for example, in presence > > of multi-queue NIC drivers (like igb or ixgbe) which binds their threads to > > particular cpus. > > > > Proposed change ("init_cpuset" loader tunable) permits changing cpu > > masks for > > userland more easily. Restricting user processes to migrate to/from CPU > > cores > > used for network traffic processing is one of the cases. > > > > Phabricator: https://phabric.freebsd.org/D141 (the same version attached > > inline) > > > > If there are no objections, I'll commit this next week. > Why is the tunable needed ? Because some people already depend on doing 'cpuset -l 0 -s 1'. It is also documented in our manpages that processes start in cpuset 1 by default so that you can use 'cpuset -l 0 -s 1' to move all processes, etc. For the stated problem (bound ithreads in drivers), I would actually like to fix ithreads that are bound to a specific CPU to create a different cpuset instead so they don't conflict with set 1. -- John Baldwin