On Wed, May 15, 2013 at 08:40:25PM +0000, Joji Mekkattuparamban (joji) wrote: > Hi Gleb, > > On a related note, does Qemu have an option to emulate RDTSC? > QEMU or KVM? With KVM guest executes RDTSC directly on CPU.
> Thanks, > Joji. > > -----Original Message----- > From: Gleb Natapov [mailto:g...@redhat.com] > Sent: Wednesday, April 24, 2013 11:57 PM > To: Joji Mekkattuparamban (joji) > Cc: Marcelo Tosatti; qemu-devel@nongnu.org; k...@vger.kernel.org > Subject: Re: [Qemu-devel] Para-Virtualized Clock Usage > > On Thu, Apr 25, 2013 at 12:28:35AM +0000, Joji Mekkattuparamban (joji) wrote: > > Thank you Gleb and Marcelo. I will migrate the API using gettimeofday. > > > > Is there any dependency on the QEMU or the Guest? If the host supports > > pvclock and the guest invokes gettimeofday, would the pvclock be > > automatically used? Or do I require a patch in either the Qemu or the guest > > kernel? > > > Guest and host kernel should be at least 3.8. IIRC there is not QEMU version > dependency. > > > Thanks! > > Joji. > > > > -----Original Message----- > > From: Marcelo Tosatti [mailto:mtosa...@redhat.com] > > Sent: Wednesday, April 24, 2013 1:28 AM > > To: Gleb Natapov > > Cc: Joji Mekkattuparamban (joji); qemu-devel@nongnu.org; > > k...@vger.kernel.org > > Subject: Re: [Qemu-devel] Para-Virtualized Clock Usage > > > > On Tue, Apr 23, 2013 at 08:52:16AM +0300, Gleb Natapov wrote: > > > On Mon, Apr 22, 2013 at 04:58:01PM +0000, Joji Mekkattuparamban (joji) > > > wrote: > > > > Greetings, > > > > > > > > I have a SMP guest application, running on the 2.6.27 Linux kernel. The > > > > application, originally written for bare metal, makes extensive use of > > > > the TSC, by directly invoking rdtsc from the user space for timestamp > > > > purposes. While running on KVM (RHEL version 6.3), we are running into > > > > TSC issues on some hardware. As a solution, I am considering migrating > > > > to the pvclock. I am wondering if there is an example for migrating > > > > from TSC to the pvclock. Any pointers? > > > > > > > Wrong list, you should ask KVM (copied). Recent kernels have pvclock > > > vdso support which means that gettimeofday() uses it without > > > entering the kernel. Marcelo? > > > > > > -- > > > Gleb. > > > > Converting application to make use of gettimeofday() should be the best way > > to make use of pvclock, yes. > > -- > Gleb. > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Gleb.
