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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7002EC433F5 for ; Tue, 8 Mar 2022 08:26:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240780AbiCHI1F (ORCPT ); Tue, 8 Mar 2022 03:27:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52950 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234091AbiCHI1E (ORCPT ); Tue, 8 Mar 2022 03:27:04 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C5E53F318 for ; Tue, 8 Mar 2022 00:26:08 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E9C35B817D4 for ; Tue, 8 Mar 2022 08:26:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPS id 9806CC340F7 for ; Tue, 8 Mar 2022 08:26:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646727965; bh=guvk9x1Op97zuzURP3QqZ9xuFIprOfjMyPIa+lWEAsc=; h=From:To:Subject:Date:In-Reply-To:References:From; b=t3hrTae4TGY+vb2jQsHaUn6k2adXAJdkW2QsLACHLr12mp00/FtJeAI8wlpqiXXJO qsDd+0k8Oio/WUZGZoHMi2q6vycg36dOfOsdS2AYeLK3mbCuJkyilw6Me0L9ieQTo+ fN8VXOY9nvSUoF713yte4JhbRAIXi2LXpcLPOoQAtQEfb7zYQ5mUp1OP8wxArNmPQW ghTed4ZCB7/237HXifLjV8RdbgwCTY/3r8BmUjMlrXnQUa2CitD4g82VJNnRCgqQWk BE0htlcRn/fUiiVnIIVbAj+4Ln4UwIMjiTtIrAh0IVJ56sNZMCB12Q9QaK5LCk7s+t +Nydu84w+0ouw== Received: by aws-us-west-2-korg-bugzilla-1.web.codeaurora.org (Postfix, from userid 48) id 86887C05FD6; Tue, 8 Mar 2022 08:26:05 +0000 (UTC) From: bugzilla-daemon@kernel.org To: kvm@vger.kernel.org Subject: [Bug 199727] CPU freezes in KVM guests during high IO load on host Date: Tue, 08 Mar 2022 08:26:05 +0000 X-Bugzilla-Reason: None X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: AssignedTo virtualization_kvm@kernel-bugs.osdl.org X-Bugzilla-Product: Virtualization X-Bugzilla-Component: kvm X-Bugzilla-Version: unspecified X-Bugzilla-Keywords: X-Bugzilla-Severity: high X-Bugzilla-Who: stefanha@gmail.com X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P1 X-Bugzilla-Assigned-To: virtualization_kvm@kernel-bugs.osdl.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugzilla.kernel.org/ Auto-Submitted: auto-generated MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org https://bugzilla.kernel.org/show_bug.cgi?id=3D199727 --- Comment #16 from Stefan Hajnoczi (stefanha@gmail.com) --- On Tue, 8 Mar 2022 at 08:01, wrote: > > https://bugzilla.kernel.org/show_bug.cgi?id=3D199727 > > --- Comment #15 from Roland Kletzing (devzero@web.de) --- > yes, i was using cache=3Dnone and io_uring also caused issues. > > >aio=3Dthreads avoids softlockups because the preadv(2)/pwritev(2)/fdatas= ync(2) > > syscalls run in worker threads that don't take the QEMU global mutex. > >Therefore vcpu threads can execute even when I/O is stuck in the kernel = due > to > >a lock. > > yes, that was a long search/journey to get to this information/params.... > > regarding io_uring - after proxmox enabled it as default, it was taken ba= ck > again after some issues had been reported. > > have look at: > https://github.com/proxmox/qemu-server/blob/master/debian/changelog > > maybe it's not ready for primetime yet !? > > -- Proxmox Support Team Fri, 30 Jul 2021 16:53:44 > +0200 > qemu-server (7.0-11) bullseye; urgency=3Dmedium > > * lvm: avoid the use of io_uring for now > > -- Proxmox Support Team Fri, 23 Jul 2021 11:08:48 > +0200 > qemu-server (7.0-10) bullseye; urgency=3Dmedium > > * avoid using io_uring for drives backed by LVM and configured for > write-back > or write-through cache > > -- Proxmox Support Team Mon, 05 Jul 2021 20:49:50 > +0200 > qemu-server (7.0-6) bullseye; urgency=3Dmedium > > * For now do not use io_uring for drives backed by Ceph RBD, with KRBD = and > write-back or write-through cache enabled, as in that case some > polling/IO > may hang in QEMU 6.0. > Changelog messages mention cache=3Dwritethrough and cache=3Dwriteback, which are both problematic because host memory pressure will interfere with guest performance. That is probably not an issue with io_uring per se, just another symptom of using cache=3Dwriteback/writethrough in cases where it's inappropriate. If you have trace data showing io_uring_enter(2) hanging with cache=3Dnone then Jens Axboe and other io_uring developers may be able to help resolve that. Stefan --=20 You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.=