From owner-svn-src-projects@FreeBSD.ORG Sat Sep 15 23:52:55 2012 Return-Path: Delivered-To: svn-src-projects@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id B02CF106564A; Sat, 15 Sep 2012 23:52:55 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from bigwig.baldwin.cx (bigknife-pt.tunnel.tserv9.chi1.ipv6.he.net [IPv6:2001:470:1f10:75::2]) by mx1.freebsd.org (Postfix) with ESMTP id 643048FC12; Sat, 15 Sep 2012 23:52:55 +0000 (UTC) Received: from John-Baldwins-MacBook-Air.local (c-68-39-198-164.hsd1.de.comcast.net [68.39.198.164]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 362E1B911; Sat, 15 Sep 2012 19:52:54 -0400 (EDT) Message-ID: <505514D5.90800@FreeBSD.org> Date: Sat, 15 Sep 2012 19:52:53 -0400 From: John Baldwin User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:15.0) Gecko/20120824 Thunderbird/15.0 MIME-Version: 1.0 To: attilio@FreeBSD.org References: <201207301350.q6UDobCI099069@svn.freebsd.org> <201209130910.50876.jhb@freebsd.org> <201209131132.21103.jhb@freebsd.org> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Sat, 15 Sep 2012 19:52:54 -0400 (EDT) Cc: Davide Italiano , mlaier@freebsd.org, svn-src-projects@freebsd.org, Konstantin Belousov , src-committers@freebsd.org, Stephan Uphoff Subject: Re: svn commit: r238907 - projects/calloutng/sys/kern X-BeenThere: svn-src-projects@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the src " projects" tree" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 15 Sep 2012 23:52:55 -0000 On 9/14/12 6:32 PM, Attilio Rao wrote: > On Thu, Sep 13, 2012 at 5:20 PM, Attilio Rao wrote: >> On 9/13/12, John Baldwin wrote: >>> On Thursday, September 13, 2012 10:38:54 am Attilio Rao wrote: >>>> On Thu, Sep 13, 2012 at 2:10 PM, John Baldwin wrote: >>>>> On Wednesday, September 12, 2012 9:36:58 pm Attilio Rao wrote: >>>>>> On Thu, Aug 2, 2012 at 10:07 PM, John Baldwin wrote: >>>>>>> On Thursday, August 02, 2012 4:56:03 pm Attilio Rao wrote: >>>>>>>> On 7/30/12, John Baldwin wrote: >>>>>>>>> --- //depot/projects/smpng/sys/kern/kern_rmlock.c 2012-03-25 >>>>>>>>> 18:45:29.000000000 0000 >>>>>>>>> +++ //depot/user/jhb/lock/kern/kern_rmlock.c 2012-06-18 >>>>>>>>> 21:20:58.000000000 >>>>>>>>> 0000 >>>>>>>>> @@ -70,6 +70,9 @@ >>>>>>>>> } >>>>>>>>> >>>>>>>>> static void assert_rm(const struct lock_object *lock, int >>>>>>>>> what); >>>>>>>>> +#ifdef DDB >>>>>>>>> +static void db_show_rm(const struct lock_object *lock); >>>>>>>>> +#endif >>>>>>>>> static void lock_rm(struct lock_object *lock, int how); >>>>>>>>> #ifdef KDTRACE_HOOKS >>>>>>>>> static int owner_rm(const struct lock_object *lock, struct >>>>>>>>> thread >>>>>>>>> **owner); >>>>>>>> >>>>>>>> While here, did you consider also: >>>>>>>> - Abstracting compiler_memory_barrier() into a MI, compiler >>>>>>>> dependent function? >>>>>>>> - Fix rm_queue with DCPU possibly >>>>>>> >>>>>>> Mostly I just wanted to fill in missing functionality and fixup the >>>>>>> RM_SLEEPABLE bits a bit. >>>>>> >>>>>> So what do you think about the following patch? If you agree I will >>>>>> send to pho@ for testing in a batch with other patches. >>>>> >>>>> It's not super clear to me that having it be static vs dynamic is all >>>>> that >>>>> big of a deal. However, your approach in general is better, and it >>>>> certainly >>>>> should have been using PCPU_GET() for the curcpu case all along rather >>>>> than >>>>> inlining pcpu_find(). >>>> >>>> You mean what is the performance difference between static vs dynamic? >>>> Or you mean, why we want such patch at all? >>>> In the former question there is a further indirection (pc_dynamic >>>> access), for the latter question the patched code avoids namespace >>>> pollution at all and makes the code more readable. >>> >>> More why we want it. I think most of your readability fixes would work >>> just >>> as well if it remained static and we used PCPU_GET(). However, I think >>> your >>> changes are fine. >> >> Well, the namespace pollution cannot be avoided without using the >> dynamic approach, and that is the important part of the patch. >> >>> FYI, much of subr_rmlock.c goes out of its way to optimize for performance >>> (such as inlining critical_enter(), critical_exit(), and pcpu_find()), so >>> adding the new indirection goes against the grain of that. >> > > I've thought about it and I think that avoiding the indirection is > sensitive in that codepath. I've then came up with this patch which > should avoid namespace pollution and the indirection. > > What do you think about it? Why not just move rm_queue to _rmlock.h and make pcpu.h include that? Barring that, make a _rmlock_queue.h and have both headers include that. However, I think that having _rmlock.h in pcpu.h is fine. -- John Baldwin