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Commit 8a22b999 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge
Browse files

xen: drop xen_sched_clock in favour of using plain wallclock time 



xen_sched_clock only counts unstolen time.  In principle this should
be useful to the Linux scheduler so that it knows how much time a process
actually consumed.  But in practice this doesn't work very well as the
scheduler expects the sched_clock time to be synchronized between
cpus.  It also uses sched_clock to measure the time a task spends
sleeping, in which case "unstolen time" isn't meaningful.

So just use plain xen_clocksource_read to return wallclock nanoseconds
for sched_clock.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
parent 31de189f

arch/x86/xen/enlighten.c

+1 −1
Original line number Diff line number Diff line
@@ -926,7 +926,7 @@ static const struct pv_init_ops xen_init_ops __initdata = { 
};



static const struct pv_time_ops xen_time_ops __initdata = {

	.sched_clock = xen_sched_clock,

	.sched_clock = xen_clocksource_read,

};



static const struct pv_cpu_ops xen_cpu_ops __initdata = {

arch/x86/xen/time.c

+0 −39
Original line number Diff line number Diff line
@@ -155,45 +155,6 @@ static void do_stolen_accounting(void) 
	account_idle_ticks(ticks);

}



/*

 * Xen sched_clock implementation.  Returns the number of unstolen

 * nanoseconds, which is nanoseconds the VCPU spent in RUNNING+BLOCKED

 * states.

 */

unsigned long long xen_sched_clock(void)

{

	struct vcpu_runstate_info state;

	cycle_t now;

	u64 ret;

	s64 offset;



	/*

	 * Ideally sched_clock should be called on a per-cpu basis

	 * anyway, so preempt should already be disabled, but that's

	 * not current practice at the moment.

	 */

	preempt_disable();



	now = xen_clocksource_read();



	get_runstate_snapshot(&state);



	WARN_ON(state.state != RUNSTATE_running);



	offset = now - state.state_entry_time;

	if (offset < 0)

		offset = 0;



	ret = state.time[RUNSTATE_blocked] +

		state.time[RUNSTATE_running] +

		offset;



	preempt_enable();



	return ret;

}





/* Get the TSC speed from Xen */

unsigned long xen_tsc_khz(void)

{