From owner-svn-src-head@FreeBSD.ORG Tue Jan 20 23:48:07 2015 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id EABC9222; Tue, 20 Jan 2015 23:48:06 +0000 (UTC) Received: from mail-yh0-x230.google.com (mail-yh0-x230.google.com [IPv6:2607:f8b0:4002:c01::230]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id AB1EFF4B; Tue, 20 Jan 2015 23:48:06 +0000 (UTC) Received: by mail-yh0-f48.google.com with SMTP id a41so5473131yho.7; Tue, 20 Jan 2015 15:48:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=ys/gb57OI3eZ7XOY7tNt1O7PLAwVgHYynV1B53vbTug=; b=xt2tt23lG0vsoVcCm230nShvB3lIG8X3sMUimbjmaiteDdMlCBBYcE4XcK/V9t3KEH nnsTGYrdSAUt3zNXCIqxKFMhxHmaNUuHBkY+a2wdR8bjvOArxoIP2M6ehN7penEe3Q4A HXcGpVL0nDQOV/RK9jL9g00LElFQE6XEUGF6ht6ddZ+F+4jKQ0X9ov1zmL1wj98cnEXT SldoSC9pyETVN6sjzsiQvG6cmMW5lKciUuhLwcAVbE/tAEO9seL3E875pWy7XJFHIlNL glMy5POfVgaE7yifoSorNZtcvOAxfM4sprLi2rh9P9b4g1HulzKyNEvbldFAl1dvA0Jc MI9Q== MIME-Version: 1.0 X-Received: by 10.236.89.172 with SMTP id c32mr22709191yhf.180.1421797685822; Tue, 20 Jan 2015 15:48:05 -0800 (PST) Sender: kmacybsd@gmail.com Received: by 10.170.70.132 with HTTP; Tue, 20 Jan 2015 15:48:05 -0800 (PST) In-Reply-To: <54BEE8E6.3080009@ignoranthack.me> References: <201501151532.t0FFWV2Y037455@svn.freebsd.org> <54BDD9E1.6090505@selasky.org> <20150120075126.GA42409@kib.kiev.ua> <20150120211137.GY15484@FreeBSD.org> <54BED6FB.8060401@selasky.org> <54BEE62D.2060703@ignoranthack.me> <54BEE8E6.3080009@ignoranthack.me> Date: Tue, 20 Jan 2015 15:48:05 -0800 X-Google-Sender-Auth: l7UP_U1iq2RWv4WgNDglT54hWB4 Message-ID: Subject: Re: svn commit: r277213 - in head: share/man/man9 sys/kern sys/ofed/include/linux sys/sys From: "K. Macy" To: Sean Bruno Content-Type: text/plain; charset=UTF-8 Cc: Hans Petter Selasky , Adrian Chadd , "src-committers@freebsd.org" , Jason Wolfe , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" , Gleb Smirnoff , Konstantin Belousov 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: Tue, 20 Jan 2015 23:48:07 -0000 Are any other drivers hitting this? e.g. cxgb/cxgbe? -K On Tue, Jan 20, 2015 at 3:46 PM, Sean Bruno wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA512 > > On 01/20/15 15:40, K. Macy wrote: >> I think you're working around driver locking bugs by crippling the >> callout code. >> >> -K >> > > We had zero evidence of this. What leads you down that path? I'm > totally open to being wrong, e.g. "yeah, you slowed down things so > that you don't hit a race condition" > > sean > >> On Tue, Jan 20, 2015 at 3:35 PM, Sean Bruno >> wrote: On 01/20/15 14:30, Hans Petter >> Selasky wrote: >>>>> On 01/20/15 22:11, Gleb Smirnoff wrote: >>>>>> On Tue, Jan 20, 2015 at 09:51:26AM +0200, Konstantin >>>>>> Belousov wrote: K> > Like stated in the manual page, >>>>>> callout_reset_curcpu/on() does not work K> > with MPSAFE >>>>>> callouts any more! K> I.e. you 'fixed' some undeterminate >>>>>> bugs in callout migration by not K> doing migration at all >>>>>> anymore. K> K> > K> > You need to use >>>>>> callout_init_{mtx,rm,rw} and remove the custom locking K> > >>>>>> inside the callback in the TCP stack to get it working like >>>>>> before! K> K> No, you need to do this, if you think that >>>>>> whole callout KPI must be K> rototiled. It is up to the >>>>>> person who modifies the KPI, to ensure that K> existing >>>>>> code is not broken. K> K> As I understand, currently we are >>>>>> back to the one-cpu callouts. K> Do other people consider >>>>>> this situation acceptable ? >>>>>> >>>>>> I think this isn't acceptable. The commit to a complex >>>>>> subsystem lacked a review from persons involved in the >>>>>> system before. The commit to subsystem broke consumers of >>>>>> the subsystem and this was even done not accidentially, but >>>>>> due to Hans not caring about it. >>>>>> >>>>>> As for me this is enough to request a backout, and let the >>>>>> change back in only after proper review. >>>>>> >>>>> >>>>> Hi Gleb, >>>>> >>>>> Backing out my callout API patch means we will for sure >>>>> re-introduce an unknown callout spinlock hang, as noted to me >>>>> by several people. What do you think about that? dram Maybe >>>>> "Jason Wolfe" CC'ed can add to 10-stable w/o my patches: >>>>> >> >> Jason picked up this patch for work and it resolved our >> instability issues that had remained unsolved for quite some time >> as reported to freebsd-net: >> >> https://lists.freebsd.org/pipermail/freebsd-net/2015-January/040895.html >> >> This had gone undiagnosed for some time (even with the gracious >> help of jhb in offline emails, thanks btw!). >> >> There's some diagnostics in that email thread that may be of value >> to you folks for determination of the validity of changing the >> callout API or at least understanding why we were involved in >> diagnostics. >> >> While I'd sure love to tune performance, the fact that our >> machines were basically going out to lunch without these changes, >> probably means that others were seeing it and didn't know what else >> to do. As much as I enjoy a good "break out the pitch forks and >> torches" email thread, this increased stability for us and is >> allowing us to upgrade from freebsd8 to freebsd10. Bear this in >> mind when you throw your voice in favor of reverting. >> >>>>> int callout_reset_sbt_on(struct callout *c, sbintime_t sbt, >>>>> sbintime_t precision, void (*ftn)(void *), void *arg, int >>>>> cpu, int flags) { sbintime_t to_sbt, pr; struct callout_cpu >>>>> *cc; int cancelled, direct; >>>>> >>>>> + cpu = timeout_cpu; /* XXX test code XXX */ >>>>> >>>>> cancelled = 0; >>>>> >> >> Jason or I would have to run this in production, which would be >> problematic I fear. We never had a deterministic test case that >> would exhibit the reported failure. We merely "tested in >> production" and saw that panics ceased. We didn't note a dropoff >> in our traffic either, perhaps we are not as efficient as others in >> this corner case, but we were consistently seeing the spinlock >> hangs after a day or so of traffic. >> >>>>> And see if he observes a callout spinlock hang or not on his >>>>> test setup. The patch above should force all callouts to the >>>>> same thread basically. Then we could maybe see if single >>>>> threading the callouts has anything to do with solving the >>>>> spinlock hang. >>>>> >>>>> The "rewritten" callout API still has all the features and >>>>> capabilities the old one had, when used as described in "man >>>>> 9 callout". >>>>> >>>>> At the present moment I'm not technically convinced a backout >>>>> is correct. >> >> Neither am I, to be honest. Just based on *results*. >> >>>>> >>>>> Gleb: I think we would see far better results with high >>>>> speed internet links using TCP if we could extend the LRO >>>>> (large receive offload) code to accumulate more than 64KBytes >>>>> worth of data per call to the TCP stack instead of >>>>> complaining about some callouts ending up on the same thread! >>>>> Actually I have a patch for that. >>>>> >>>>> --HPS >>>>> >>>>> >>>>> >> >>> _______________________________________________ >>> svn-src-head@freebsd.org mailing list >>> http://lists.freebsd.org/mailman/listinfo/svn-src-head To >>> unsubscribe, send any mail to >>> "svn-src-head-unsubscribe@freebsd.org" >> >> > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v2 > > iQF8BAEBCgBmBQJUvujmXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w > ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRCQUFENDYzMkU3MTIxREU4RDIwOTk3REQx > MjAxRUZDQTFFNzI3RTY0AAoJEBIB78oecn5kv2MH/1F15x/lgwWq5fE/cZ3n9HlV > 9Nd7DU03coj9qUU6LH1eLPPuUn7yelCw8xxtb0qOTIDyrzNYe+HIaJi1GMHkV8Ve > iKFuB1G9gcN/nQ5BdaAezOazEUcRY2msigMh5n/2X/UDRzLAGfhbDFbogpRy1TyI > fqKzYDM8Mx9yZfCuc4/yBUVmxDcVn6NsuQ7CW745qXQcrELdJ8fjKfaYWbprCR7u > xA3Iwiio9Bv0/8MvR9n3PZ8z3NjAKD1XxV5iAPI+ANc/5Rc60cSmtP0mQakqOoz6 > 8uucaus79KdykdNovh31ka0dp0JBCghZOsfNXP69TFfvSXyngMZqwZgqVLVcX3M= > =0AV4 > -----END PGP SIGNATURE-----