Messages in this thread | | | Date | Tue, 23 Dec 2014 10:25:49 -0500 | From | Boris Ostrovsky <> | Subject | Re: [Xen-devel] [RFC 2/2] x86, vdso, pvclock: Simplify and speed up the vdso pvclock reader |
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On 12/23/2014 10:14 AM, Paolo Bonzini wrote: > > 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).
Right, I didn't notice that.
-boris
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