Messages in this thread | | | Date | Tue, 23 Dec 2014 16:14:11 +0100 | From | Paolo Bonzini <> | Subject | Re: [Xen-devel] [RFC 2/2] x86, vdso, pvclock: Simplify and speed up the vdso pvclock reader |
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On 23/12/2014 16:14, Boris Ostrovsky wrote: >> + do { >> + version = pvti->version; >> + >> + /* This is also a read barrier, so we'll read version first. */ >> + rdtsc_barrier(); >> + tsc = __native_read_tsc(); > > > This will cause VMEXIT on Xen with TSC_MODE_ALWAYS_EMULATE which is > used, for example, after guest migrated (unless HW is capable of scaling > TSC rate).
So does the __pvclock_read_cycles this is replacing (via pvclock_get_nsec_offset).
Paolo
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