On Mon, Nov 24, 2014 at 1:48 PM, Konrad Rzeszutek Wilk <konrad.w...@oracle.com> 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 <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!
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-de...@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 (<sad trombone played > from YouTube>). OK. I'll try and do better at keeping up with things. 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/
