On Wed, 3 May 2017 12:28:35 -0400 Nick Sarnie <commendsarnex@xxxxxxxxx> wrote: > On Wed, May 3, 2017 at 10:37 AM, Matthias Ehrenfeuchter <efeu@xxxxxxxxxx> wrote: > > Hi, > > > > There are a lot of messages/threads out there about bad performance while > > using AMDs Ryzen with KVM GPU passthrough. It revolves all on > > enabling/disabling npt, while enabled overall VM performance is nice but the > > GPU performance gives me about 20% (and a lot of drops to zero GPU usage, > > while CPU/Disk/Ram also doing nothing) compared to npt disabled. But while > > npt is disabled overall VM performance is like beeing on 4x86 with floppy > > disk as only storage. (Ex. it takes 2 seconds just to open startmenu while > > host and vm are in idle, and neither CPU pinning, changing CPU model, > > changing storage device nor using hugepages changed anything). > > > > So everything I read pointed to a bug in the npt implementation? Anything I > > could do to get closer to the "thing" issuing this? > > > > Best Regards > > > > efeu > > _______________________________________________ > > iommu mailing list > > iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx > > https://lists.linuxfoundation.org/mailman/listinfo/iommu > > I heard from Joerg that it might be related to a lower intercept rate > being used when NPT is enabled, but we haven't been able to find a way > to trace that to confirm. Joerg/Paolo, any ideas how we might debug this? Anyone from AMD watching? Thanks, Alex
