Anthony Liguori wrote: >>> >>> That's a bit more ambitious than I was thinking. I would be very >>> happy with a pv timer, interrupt controller, and some basic CPU >>> optimizations. I'm still not convinced the perf benefits of direct >>> paging justify the annoyances that come with it (guests being aware >>> of pfns). >> >> I thought that with paravirt_ops, all the awareness is limited to the >> paravirt implementation, and nothing in the core kernel is actually >> aware of host pfns. > > The pv_ops implementation still has to deal with guest pfn => host pfn > translation. This means that a guest has to be put into a special > mode for save/restore/migrate to work to ensure that no host pfn's are > on the stack or in registers. Changing save/restore/migration to from > guest-transparent to guest-interactive is a big loss to me.
I think it can be done without guest awareness, by having a special code section where the translation is done. The hypervisor can choose not to transfer control when rip points there. >>> This is especially true with NPT/EPT right around the corner. >> >> It depends on the workload. It was advanced (by Ingo) that NPT/EPT >> increase the tlb miss latency, which is important for steady-state >> workloads, whereas shadow and direct paging do not. It will be >> interesting to measure this. > > There will most certainly be trade-offs, but I certainly don't expect > direct paging to beat out NPT/EPT in certain areas. Sure. Like I said, we'll need measurements to decide this. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
