From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5951C4363D for ; Fri, 25 Sep 2020 01:13:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96542207C3 for ; Fri, 25 Sep 2020 01:13:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726829AbgIYBNT (ORCPT ); Thu, 24 Sep 2020 21:13:19 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:35721 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726700AbgIYBNS (ORCPT ); Thu, 24 Sep 2020 21:13:18 -0400 Received: from callcc.thunk.org (pool-72-74-133-215.bstnma.fios.verizon.net [72.74.133.215]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 08P1DBpp010998 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 24 Sep 2020 21:13:12 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 80C2E42003C; Thu, 24 Sep 2020 21:13:11 -0400 (EDT) Date: Thu, 24 Sep 2020 21:13:11 -0400 From: "Theodore Y. Ts'o" To: Ming Lei Cc: Jens Axboe , linux-ext4@vger.kernel.org, "linux-kernel@vger.kernel.org" , linux-block@vger.kernel.org, Linus Torvalds Subject: Re: REGRESSION: 37f4a24c2469: blk-mq: centralise related handling into blk_mq_get_driver_tag Message-ID: <20200925011311.GJ482521@mit.edu> References: <20200904035528.GE558530@mit.edu> <20200915044519.GA38283@mit.edu> <20200915073303.GA754106@T590> <20200915224541.GB38283@mit.edu> <20200915230941.GA791425@T590> <20200916202026.GC38283@mit.edu> <20200917022051.GA1004828@T590> <20200917143012.GF38283@mit.edu> <20200924005901.GB1806978@T590> <20200924143345.GD482521@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200924143345.GD482521@mit.edu> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 24, 2020 at 10:33:45AM -0400, Theodore Y. Ts'o wrote: > HOWEVER, thanks to a hint from a colleague at $WORK, and realizing > that one of the stack traces had virtio balloon in the trace, I > realized that when I switched the GCE VM type from e1-standard-2 to > n1-standard-2 (where e1 VM's are cheaper because they use > virtio-balloon to better manage host OS memory utilization), problem > has become, much, *much* rarer (and possibly has gone away, although > I'm going to want to run a lot more tests before I say that > conclusively) on my test setup. At the very least, using an n1 VM > (which doesn't have virtio-balloon enabled in the hypervisor) is > enough to unblock ext4 development. .... and I spoke too soon. A number of runs using -rc6 are now failing even with the n1-standard-2 VM, so virtio-ballon may not be an indicator. This is why debugging this is frustrating; it is very much a heisenbug --- although 5.8 seems to work completely reliably, as does commits before 37f4a24c2469. Anything after that point will show random failures. :-( - Ted