Messages in this thread Patch in this message | | | Date | Fri, 06 Aug 2010 11:57:22 -0700 | From | Greg KH <> | Subject | [27/34] xen: drop xen_sched_clock in favour of using plain wallclock time |
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2.6.32-stable review patch. If anyone has any objections, please let us know.
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From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
commit 8a22b9996b001c88f2bfb54c6de6a05fc39e177a upstream.
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: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/x86/xen/enlighten.c | 2 +- arch/x86/xen/time.c | 39 --------------------------------------- 2 files changed, 1 insertion(+), 40 deletions(-)
--- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -924,7 +924,7 @@ static const struct pv_init_ops xen_init }; 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 = { --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -154,45 +154,6 @@ 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) {
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