From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754764AbaKXTHL (ORCPT ); Mon, 24 Nov 2014 14:07:11 -0500 Received: from mail-ob0-f182.google.com ([209.85.214.182]:36256 "EHLO mail-ob0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754351AbaKXTHF (ORCPT ); Mon, 24 Nov 2014 14:07:05 -0500 MIME-Version: 1.0 In-Reply-To: <20141124184856.GA9349@laptop.dumpdata.com> References: <20141121142301.564f7eb7@gandalf.local.home> <20141124184856.GA9349@laptop.dumpdata.com> Date: Mon, 24 Nov 2014 14:07:04 -0500 X-Google-Sender-Auth: cqMGhNndotkAxBhm678MzyR4c6Q Message-ID: Subject: Re: frequent lockups in 3.18rc4 From: Josh Boyer To: Konrad Rzeszutek Wilk Cc: Andy Lutomirski , Linus Torvalds , Steven Rostedt , Tejun Heo , "linux-kernel@vger.kernel.org" , Thomas Gleixner , Peter Zijlstra , Frederic Weisbecker , Don Zickus , Dave Jones , "the arch/x86 maintainers" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 24, 2014 at 1:48 PM, Konrad Rzeszutek Wilk wrote: > On Fri, Nov 21, 2014 at 03:23:13PM -0500, Josh Boyer wrote: >> On Fri, Nov 21, 2014 at 3:16 PM, Andy Lutomirski wrote: >> > On Fri, Nov 21, 2014 at 12:14 PM, Josh Boyer wrote: >> >> On Fri, Nov 21, 2014 at 2:52 PM, Andy Lutomirski wrote: >> >>> On Fri, Nov 21, 2014 at 11:46 AM, Linus Torvalds >> >>> wrote: >> >>>> On Fri, Nov 21, 2014 at 11:34 AM, Linus Torvalds >> >>>> wrote: >> >>>>> >> >>>>> So I kind of agree, but it wouldn't be my primary worry. My primary >> >>>>> worry is actually paravirt doing something insane. >> >>>> >> >>>> Btw, on that tangent, does anybody actually care about paravirt any more? >> >>>> >> >>> >> >>> Amazon, for better or for worse. > > And distros: Oracle and Novell. > >> >>> >> >>>> I'd love to start moving away from it. It makes a lot of the low-level >> >>>> code completely impossible to follow due to the random indirection >> >>>> through "native" vs "paravirt op table". Not just the page table >> >>>> handling, it's all over. >> >>>> >> >>>> Anybody who seriously does virtualization uses hw virtualization that >> >>>> is much better than it used to be. And the non-serious users aren't >> >>>> that performance-sensitive by definition. > > I would point out that the PV paravirt spinlock gives an huge boost > for virtualization guests (this is for both KVM and Xen). >> >>>> >> >>>> I note that the Fedora kernel config seems to include paravirt by >> >>>> default, so you get a lot of the crazy overheads.. > > Not that much. We ran benchmarks and it was in i-cache overhead - and > the numbers came out to be sub-1% percent. >> >>> >> >>> I think that there is a move toward deprecating Xen PV in favor of >> >>> PVH, but we're not there yet. >> >> >> >> A move where? The Xen stuff in Fedora is ... not paid attention to >> >> very much. If there's something we should be looking at turning off >> >> (or on), we're happy to take suggestions. >> > >> > A move in the Xen project. As I understand it, Xen wants to deprecate >> > PV in favor of PVH, but PVH is still experimental. >> >> OK. >> >> > I think that dropping PARAVIRT in Fedora might be a bad idea for >> > several more releases, since that's likely to break the EC2 images. >> >> Yes, that's essentially the only reason we haven't looked at disabling >> Xen completely for a while now, so . > > Heh. Didn't know you could play on a trombone! It's sad because I can't really play the trombone and it sounds horrible. > As I had mentioned in the past - if there are Xen related bugs on > Fedora please CC me on them. Or perhaps CC xen-devel@lists.xenproject.org > if that is possible. Indeed, you have been massively helpful. My comment on it being not well paid attention to was a reflection on the distro maintainers, not you. You've been great once we notice the Xen issue, but that takes a while on our part and it isn't the best of user experiences :\. > And as Andy has mentioned - we are moving towards using PVH as a way > to not use the PV MMU ops. But that is still off ( from YouTube>). OK. I'll try and do better at keeping up with things. josh