Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754682AbaKXStx (ORCPT ); Mon, 24 Nov 2014 13:49:53 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:23479 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754530AbaKXStv (ORCPT ); Mon, 24 Nov 2014 13:49:51 -0500 Date: Mon, 24 Nov 2014 13:48:56 -0500 From: Konrad Rzeszutek Wilk To: Josh Boyer 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 Subject: Re: frequent lockups in 3.18rc4 Message-ID: <20141124184856.GA9349@laptop.dumpdata.com> References: <20141121142301.564f7eb7@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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! 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. 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 (). > > josh > -- > 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/ -- 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/