From owner-svn-src-head@FreeBSD.ORG Tue Jan 20 23:40:16 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 B130AD84; Tue, 20 Jan 2015 23:40:16 +0000 (UTC) Received: from mail-yk0-x22b.google.com (mail-yk0-x22b.google.com [IPv6:2607:f8b0:4002:c07::22b]) (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 646ABE86; Tue, 20 Jan 2015 23:40:16 +0000 (UTC) Received: by mail-yk0-f171.google.com with SMTP id 10so5243861ykt.2; Tue, 20 Jan 2015 15:40:15 -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=9bFAJdLE5sFn/ThVb+TOCqf1rdErdUTB70w1x4Hb+5k=; b=KMiIi1NBsXq/GhqiyUb+NOP6oztJE6fkuJcIHStzEe5aKSznP72DSm9srnuKHe17ZY fSAeQaHySrs2/jRMzNpC+e/HWtccwLH2mTmcascaasAuFERB7eB/GxzRL1qAu9714kOE Ujj/D0uyVDM/TW6g4G5gJckg+DWJUNerLdkCjPQVq3M+fLQjMCN2uk77tjG6Y274wAe4 aoMUpBBDxKqgVRqRYutr7OB/9BYQcVfVg6YH6rj22/qRRlSl2fwu13sU1KD6GfHCy15l dxHs5jRUSf+Vrbcg/BIUfgU1ivRfeCaDGz6NjPjUbNeMPl6n38Shud+pymCIfwNRY4ii 6QJw== MIME-Version: 1.0 X-Received: by 10.170.57.143 with SMTP id 137mr8189323ykz.10.1421797215562; Tue, 20 Jan 2015 15:40:15 -0800 (PST) Sender: kmacybsd@gmail.com Received: by 10.170.70.132 with HTTP; Tue, 20 Jan 2015 15:40:15 -0800 (PST) In-Reply-To: <54BEE62D.2060703@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> Date: Tue, 20 Jan 2015 15:40:15 -0800 X-Google-Sender-Auth: TCMvssV_b-y4xnPC2DU8I4XNojY 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 23:40:16 -0000 I think you're working around driver locking bugs by crippling the callout code. -K On Tue, Jan 20, 2015 at 3:35 PM, Sean Bruno wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA512 > > 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 >> >> >> > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v2 > > iQF8BAEBCgBmBQJUvuYrXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w > ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRCQUFENDYzMkU3MTIxREU4RDIwOTk3REQx > MjAxRUZDQTFFNzI3RTY0AAoJEBIB78oecn5kJTMIAMfh6ghV/AwQauY+a44q1hjJ > WC7E3u69FK0opgSYg71kk6HckbyB+sTWND6HdXnpyrcMLXUt74zlB8c48wbUUV5+ > EwKNYzGNNnDNhoc0WtPMect8e9Y1kBRvSGfHBdVrqATXfPOyZEa+i4lQAXpiFKIt > nndqVrAH7bJM6143YDpnIg7vaR+8IQnC2ztSP4ogJzh03DZ7zVsg4BsoCPg50eVZ > kr46cXcE+SP/TsQBsVNVwRJD5NFie6QJdLoTnwkd0XfQGJMIWivNgUcE4tIxqPIf > nGQ0xMJCotpNLuPtzYzCIurSaDHdHmL6bjkhjTtBmWsMNfdGH8TKoih79GDxkTg= > =Y3rd > -----END PGP SIGNATURE----- > _______________________________________________ > 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"