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=-4.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 03C04C4338F for ; Fri, 20 Aug 2021 17:25:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4A766115B for ; Fri, 20 Aug 2021 17:25:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232738AbhHTR0F (ORCPT ); Fri, 20 Aug 2021 13:26:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:55502 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232585AbhHTR0E (ORCPT ); Fri, 20 Aug 2021 13:26:04 -0400 Received: by mail.kernel.org (Postfix) with ESMTPS id 7702D61157 for ; Fri, 20 Aug 2021 17:25:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1629480326; bh=HMiNn4FxpVvGW+XUjLcjnIib8sYIGSF0TPfEOqe6jqQ=; h=From:To:Subject:Date:In-Reply-To:References:From; b=mdKZ+ypVsT4uksRv/gEYx93tNv872+a6QplQfa++oNzctaZ6NuhMgaefTkIqga1aw 6lAuk3F0Br01jwQL5ojVgRqKtpKsPCpYX8b0554qpHdCf5nnZVIGJnyuMruCoXVcm2 nSOrlHChHOa0a0vh92b0Hlyxg3ABlM5bUB5CLoxnuG7RgX0KUBfD0oAlKtIRdf1Vob 0ZyDS28N/QjpLY+Zlip1CB8BGLCEZKJx88u+BZDd94lf2sdjwru/jJIs0tl0MI6xJd PaqJBX5a+B5BksBp1hInoOwBh++IUgCQvR+eij6On8mOHlSgINK92F6xCDttZczPFa ysLW5KkM8hiAQ== From: bugzilla-daemon@bugzilla.kernel.org To: kvm@vger.kernel.org Subject: [Bug 199727] CPU freezes in KVM guests during high IO load on host Date: Fri, 20 Aug 2021 17:25:26 +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: devzero@web.de 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: cc 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 Roland Kletzing (devzero@web.de) changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |devzero@web.de --- Comment #1 from Roland Kletzing (devzero@web.de) --- i can confirm there is a severe issue here, which renders kvm/proxmox virtu= ally unusable when you have significantly io loaded hosts, i.e. if there is lots= of write io on the host or guest. whenever you get into a situation when the disk io where the vm resides on = is getting saturated, the VMs start going nuts and getting hiccup, i.e. severe latency is getting added to the guests.=20 they behave "jumpy", you can't use the console or they are totaly sluggish, ping goes up above 10secs , kernel throws "BUG: soft lockup - CPU#X stuck f= or XXs!" and such... i have found that with cache=3Dwriteback for the virtual machines disk which reside on the appropriate hdd wich heavy io, things go much much more smoot= hly.=20 without cache=3Dwriteback , live migration/move could make a guest go crazy. now with cache=3Dwriteback i could do 3 live migrations in parallel , even = with lots of io inside the virtual machines, and even with additional writer/rea= der in the host os (dd from/to the disk - ping to the guests mostly is <5ms. so, to me this problem appears to be related to disk io saturation and prob= ably related to sync writes, what else can explain that cache=3Dwriteback helps = so much ? --=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.=