Lines Matching refs:it
30 and apps that are high-TSC-frequency are usually aware of it.)
34 If the OS/app does use rdtsc, will it behave incorrectly if "time goes
36 we call this a "TSC-sensitive" app or OS; otherwise it is "TSC-resilient".
40 This last is the US$64,000 question as it may be very difficult
65 TSC-sensitive apps are running and it is necessary to understand
70 This is the same as prior to Xen 4.0 and is the best choice if it
122 every processor cycle, but on recent processors, it increases
126 so it is often used as a foundation for performance monitoring.
127 And since it is guaranteed to be monotonically increasing and, at
128 64 bits, is guaranteed to not wraparound within 10 years, it is
136 TSC again, it might appear that "time went backwards". This loss of
165 TSC but use it in a way that monotonicity and frequency invariance
172 may be "safe" on one machine, it is essentially impossible to precisely
199 where it is certain that all apps are TSC-resilient (e.g.
204 hardware on which the virtual machine is launched. If it is
205 TSC-safe, rdtsc will execute at hardware speed; if it is not, rdtsc
217 This mode (tsc_mode==3) is called PVRDTSCP, because it requires
218 app paravirtualization (awareness by the app that it may be running
221 (The rdtscp instruction differs from the rdtsc instruction in that it
230 PVRDTSCP (tsc_mode==3) has two limitations. First, it applies to
243 or a tsc_mode==3 domain when it is running on TSC-unsafe hardware.
246 it does not ensure that it continues to tick at the same rate during
257 ensures that the TSC is "safe", that is it will increment at a constant rate
267 a virtualized environment, since it is not possible to synchronize TSC
269 TSC as a usable clocksource; while time will not go backwards, it may
272 to a guest OS if it is certain that the domain will never migrate.
284 cpuid instruction execute it directly, without a trap to Xen. As a result,
323 determining if it is currently running on Xen, next whether
324 the tsc_mode setting of the domain in which it is running,
334 TSC-sensitive high-TSC-frequency apps may find it useful to
345 guest TSC frequency will be the same as the host. If it is later