On Fri, Nov 21, 2014 at 03:23:13PM -0500, Josh Boyer wrote: > On Fri, Nov 21, 2014 at 3:16 PM, Andy Lutomirski <l...@amacapital.net> wrote: > > On Fri, Nov 21, 2014 at 12:14 PM, Josh Boyer <jwbo...@fedoraproject.org> > > wrote: > >> On Fri, Nov 21, 2014 at 2:52 PM, Andy Lutomirski <l...@amacapital.net> > >> wrote: > >>> On Fri, Nov 21, 2014 at 11:46 AM, Linus Torvalds > >>> <torva...@linux-foundation.org> wrote: > >>>> On Fri, Nov 21, 2014 at 11:34 AM, Linus Torvalds > >>>> <torva...@linux-foundation.org> 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 <sad trombone>. 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-de...@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 (<sad trombone played from YouTube>). > > josh > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
