Messages in this thread | | | Date | Mon, 02 Apr 2007 00:06:22 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [patch 17/17] Add a sched_clock paravirt_op |
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Andi Kleen wrote: > Do you also get a clock for stolen nanoseconds? >
What you actually get is how many ns the CPU spent in each state. Stolen is runnable+offline.
> No need for cycles, you could just subtract the stolen ns if you > can get those.
It just seems like a simpler interface to just allow overriding sched_clock, rather than exposing sched_clock's internals and fiddling with those. There's really nothing in the existing sched_clock which can be profitably reused in the Xen case. VMI can make use of the cycles_2_ns conversion, which is why I made it available for its use.
To be specific, this is the whole Xen sched_clock function:
/* Xen sched_clock implementation. Returns the number of RUNNING ns */ unsigned long long xen_sched_clock(void) { struct vcpu_runstate_info state; cycle_t now; unsigned long long ret;
preempt_disable();
now = xen_clocksource_read(); get_runstate_snapshot(&state); WARN_ON(state.state != RUNSTATE_running);
ret = state.time[RUNSTATE_running] + (now - state.state_entry_time);
preempt_enable();
return ret; }
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