From owner-cvs-src@FreeBSD.ORG Sat Jun 12 06:42:04 2004 Return-Path: Delivered-To: cvs-src@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6352F16A4CE; Sat, 12 Jun 2004 06:42:04 +0000 (GMT) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0F25043D48; Sat, 12 Jun 2004 06:42:04 +0000 (GMT) (envelope-from scottl@freebsd.org) Received: from freebsd.org (junior-wifi.samsco.home [192.168.0.11]) (authenticated bits=0) by pooker.samsco.org (8.12.11/8.12.10) with ESMTP id i5C6iD0i013950; Sat, 12 Jun 2004 00:44:14 -0600 (MDT) (envelope-from scottl@freebsd.org) Message-ID: <40CAA578.2060808@freebsd.org> Date: Sat, 12 Jun 2004 00:40:56 -0600 From: Scott Long User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.6) Gecko/20040304 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Nate Lawson References: <200406102134.i5ALYcNr004704@repoman.freebsd.org> <20040611012513.GI78955@elvis.mu.org> <20040611232939.F3249@root.org> In-Reply-To: <20040611232939.F3249@root.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, hits=0.0 required=3.8 tests=none autolearn=no version=2.63 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on pooker.samsco.org cc: cvs-src@freebsd.org cc: Alfred Perlstein cc: Robert Watson cc: src-committers@freebsd.org cc: cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/kern uipc_usrreq.c X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 12 Jun 2004 06:42:04 -0000 Nate Lawson wrote: > On Thu, 10 Jun 2004, Alfred Perlstein wrote: > >>* Robert Watson [040610 14:34] wrote: >> >>> - Sam's version of this change, as with the BSD/OS version, made use of >>> both a global lock and per-unpcb locks. However, in practice, the >>> global lock covered all accesses, so I have simplified out the unpcb >>> locks in the interest of getting this merged faster (reducing the >>> overhead but not sacrificing granularity in most cases). We will want >>> to explore possibilities for improving lock granularity in this code in >>> the future. >> >>I noticed this in the BSD/os version, it was sort of like... >>"the global lock covers everything, what's the point of the >>underlying locks..?" > > > In my conversation with the BSD/OS guys, there were often cases where they > went with a more global lock within a subsystem versus untangling > re-entrant paths, which would be needed for finer-grained locking. This > was true for the CAM approach they used where a single mutex per device > instance and a middle layer lock protected queue handling. > > -Nate Yes, but as this approach was described to me, I'm not terribly sure that it would work in an environment with multiple SIMs. I appreciate their approach of 'medium-grain locking' a lot, but I question whether their approach to CAM and to network locking was really sufficient. Scott