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 90E62C4338F for ; Sat, 21 Aug 2021 08:53:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61DF76108F for ; Sat, 21 Aug 2021 08:53:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233147AbhHUIx5 (ORCPT ); Sat, 21 Aug 2021 04:53:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:47368 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232802AbhHUIx5 (ORCPT ); Sat, 21 Aug 2021 04:53:57 -0400 Received: by mail.kernel.org (Postfix) with ESMTPS id 8ADB961186 for ; Sat, 21 Aug 2021 08:53:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1629535997; bh=E6TZuGRlp5RRbuvkVF71XzqBtfChK8lwjsad0AHgHkU=; h=From:To:Subject:Date:In-Reply-To:References:From; b=RN/MaR/EbDW7vJl0M61RnGTPOK3EccUL0yFAE1XcdIBpW6GvjaxWCDDdsZA8Dlvw8 EMRQrAk/v8tjTXLGuT5l22lcrsfb+QpqJYg3s44D3DHAsDszCQqHnD9g2pQmTuLBzj VbauYmJCm9WMH/X9z+N+JoBNjhozopz74VLmZhdBOg+5nbjW/OMqIQ5f9nfnxucxv4 KS37DyZ3AVoWVoBM0UpFbvIne4tqlk72s+clpZ5uILyx/YSerpYlChGikpH/pKuLG2 El5MpR6rR0xHhJm8TgGm00gL6MIl2TgO9jWhArnA1oZx4Fdfk53Llq5w9o4pO85vUY oIHpt2WfbK/Uw== 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: Sat, 21 Aug 2021 08:53:17 +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: 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 #3 from Roland Kletzing (devzero@web.de) --- i had a look at kvm process with strace.=20 with virtual disk caching option set to "Default (no cache)", kvm is doing = IO submission via io_submit() instead of pwritev(), and apparently that can be= a long blocking call. i see whenever the VM getting hickup and pingtime goes through the roof, th= ere is long blocking io_submit() operation in progress=20 looks like a "design issue" to me and "Default (no cache)" thus being a bad default setting. see: https://lwn.net/Articles/508064/ and=20 https://stackoverflow.com/questions/34572559/asynchronous-io-io-submit-late= ncy-in-ubuntu-linux --=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.=