Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757261AbbLAWsG (ORCPT ); Tue, 1 Dec 2015 17:48:06 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:30176 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756465AbbLAWsD (ORCPT ); Tue, 1 Dec 2015 17:48:03 -0500 Subject: Re: [Xen-devel] linux 4.4 Regression: 100% cpu usage on idle pv guest under Xen with single vcpu. To: Sander Eikelenboom References: <80dcf47eb772c65a62652d7a56c8ed26@eikelenboom.it> <20151130214513.GF14317@char.us.oracle.com> <16a638d3c5e24963599e621f265181f8@eikelenboom.it> <565CD3A7.1060006@oracle.com> <1454b921884da94b7c1e9f434c13eb4a@eikelenboom.it> Cc: Konrad Rzeszutek Wilk , david.vrabel@citrix.com, linux-kernel@vger.kernel.org, xen-devel@lists.xen.org From: Boris Ostrovsky Message-ID: <565E239E.8070507@oracle.com> Date: Tue, 1 Dec 2015 17:47:58 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <1454b921884da94b7c1e9f434c13eb4a@eikelenboom.it> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2174 Lines: 64 On 11/30/2015 05:55 PM, Sander Eikelenboom wrote: > On 2015-11-30 23:54, Boris Ostrovsky wrote: >> On 11/30/2015 04:46 PM, Sander Eikelenboom wrote: >>> On 2015-11-30 22:45, Konrad Rzeszutek Wilk wrote: >>>> On Sat, Nov 28, 2015 at 04:47:43PM +0100, Sander Eikelenboom wrote: >>>>> Hi all, >>>>> >>>>> I have just tested a 4.4-rc2 kernel (current linus tree) + the tip >>>>> tree >>>>> pulled on top. >>>>> >>>>> Running this kernel under Xen on PV-guests with multiple vcpus >>>>> goes well (on >>>>> idle < 10% cpu usage), >>>>> but a guest with only a single vcpu doesn't idle at all, it seems >>>>> a kworker >>>>> thread is stuck: >>>>> root 569 98.0 0.0 0 0 ? R 16:02 12:47 >>>>> [kworker/0:1] >>>>> >>>>> Running a 4.3 kernel works fine with a single vpcu, bisecting >>>>> would probably >>>>> quite painful since there were some breakages this merge window >>>>> with respect >>>>> to Xen pv-guests. >>>>> >>>>> There are some differences in the diff's from booting a 4.3, >>>>> 4.4-single, >>>>> 4.4-multi cpu boot: >>>> >>>> Boris has been tracking a bunch of them. I am attaching the latest >>>> set of >>>> patches I've to carry on top of v4.4-rc3. >>> >>> Hi Konrad, >>> >>> i will test those, see if it fixes all my issues and report back >> >> They shouldn't help you ;-( (and I just saw a message from you >> confirming this) >> >> The first one fixes a 32-bit bug (on bare metal too). The second fixes >> a fatal bug for 32-bit PV guests. The other two are code >> improvements/cleanup. > > One of these patches also fixes a bug i was having with a > pci-passthrough device in > a HVM that wasn't working (depending on which dom0-kernel i was using > (4.3 or 4.4)), > but didn't report yet. > > Fingers crossed but i think this pv-guest single vcpu issue is the > last i'm troubled by for now ;) I could not reproduce this, including with your kernel config file. -boris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/