From owner-svn-src-head@FreeBSD.ORG Sun Nov 2 21:38:25 2014 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 590F23DF; Sun, 2 Nov 2014 21:38:25 +0000 (UTC) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id D09BB92F; Sun, 2 Nov 2014 21:38:24 +0000 (UTC) Received: from tom.home (kostik@localhost [127.0.0.1]) by kib.kiev.ua (8.14.9/8.14.9) with ESMTP id sA2LcJX7045261 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sun, 2 Nov 2014 23:38:19 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.9.2 kib.kiev.ua sA2LcJX7045261 Received: (from kostik@localhost) by tom.home (8.14.9/8.14.9/Submit) id sA2LcJXG045260; Sun, 2 Nov 2014 23:38:19 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Sun, 2 Nov 2014 23:38:19 +0200 From: Konstantin Belousov To: Attilio Rao Subject: Re: svn commit: r273966 - in head: share/man/man9 sys/kern sys/sys Message-ID: <20141102213819.GF53947@kib.kiev.ua> References: <201411021310.sA2DAWmD003298@svn.freebsd.org> <20141102163728.GX53947@kib.kiev.ua> <20141102165916.GY53947@kib.kiev.ua> <20141102174958.GZ53947@kib.kiev.ua> <20141102191029.GA53947@kib.kiev.ua> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.0 X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on tom.home Cc: "svn-src-head@freebsd.org" , "svn-src-all@freebsd.org" , "src-committers@freebsd.org" X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 02 Nov 2014 21:38:25 -0000 On Sun, Nov 02, 2014 at 10:17:26PM +0100, Attilio Rao wrote: > On Sun, Nov 2, 2014 at 8:10 PM, Konstantin Belousov wrote: > > On Sun, Nov 02, 2014 at 06:53:44PM +0100, Attilio Rao wrote: > >> > I did not proposed to verify owner chain. I said that it is easy to > >> > record the locks owned by current thread, only for current thread > >> > consumption. Below is the prototype. > >> > >> I think it is too expensive, think that this must happen for every shared lock. > >> I know we may not be using too many shared locks on lockmgr right now, > >> but it is not a good reason to make shared lock bloated and more > >> expensive on lockmgr. > > > > It can be significantly simplified, if the array of lock pointers is > > kept dense. Then the only non-trivial operation is unlock out of order, > > when the array have to be compacted. > > > > The code adds one write and n reads on shared lock, where n is the > > number of shared-locked locks already owned by thread. Typical n is 0 > > or 1. On unlock, if done in order, the code adds one read; unordered > > unlock shuffles array elements. Again, for typical lock nesting of 2, > > this means one read and one write, and even this is rare. All reads and > > writes are for thread-local memory. > > > > I am not going to spend any more time on this if people do not consider > > the lock tracking worth it. Otherwise, I will benchmark the patch. > > I think that your initial patch (what is in head now) is a better approach. > I would just make it a lockinit() flag to make it less alien to the KPI. > Ok. Can you explain what would the proposed lockinit() flag do ? What should it change comparing with the current code ?