This accounts for the time Xen steals from our VCPUs. This accounting gets run on each timer interrupt, just as a way to get it run relatively often, and when interesting things are going on. Stolen time is not really used by much in the kernel; it is reported in /proc/stats, and that's about it. Signed-off-by: Jeremy Fitzhardinge Acked-by: Chris Wright Cc: john stultz Cc: Rik van Riel --- arch/i386/xen/time.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 105 insertions(+), 1 deletion(-) =================================================================== --- a/arch/i386/xen/time.c +++ b/arch/i386/xen/time.c @@ -2,6 +2,7 @@ #include #include #include +#include #include #include @@ -14,6 +15,7 @@ #define XEN_SHIFT 22 #define TIMER_SLOP 100000 /* Xen may fire a timer up to this many ns early */ +#define NS_PER_TICK (1000000000ll / HZ) /* These are perodically updated in shared_info, and then copied here. */ struct shadow_time_info { @@ -26,6 +28,104 @@ struct shadow_time_info { static DEFINE_PER_CPU(struct shadow_time_info, shadow_time); +/* runstate info updated by Xen */ +static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate); + +/* snapshots of runstate info */ +static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate_snapshot); + +/* unused ns of stolen and blocked time */ +static DEFINE_PER_CPU(u64, residual_stolen); +static DEFINE_PER_CPU(u64, residual_blocked); + +/* + * Runstate accounting + */ +static void get_runstate_snapshot(struct vcpu_runstate_info *res) +{ + u64 state_time; + struct vcpu_runstate_info *state; + + preempt_disable(); + + state = &__get_cpu_var(runstate); + + /* + * The runstate info is always updated by the hypervisor on + * the current CPU, so there's no need to use anything + * stronger than a compiler barrier when fetching it. + */ + do { + state_time = state->state_entry_time; + barrier(); + *res = *state; + barrier(); + } while(state->state_entry_time != state_time); + + preempt_enable(); +} + +static void setup_runstate_info(void) +{ + struct vcpu_register_runstate_memory_area area; + + area.addr.v = &__get_cpu_var(runstate); + + if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, + smp_processor_id(), &area)) + BUG(); + + get_runstate_snapshot(&__get_cpu_var(runstate_snapshot)); +} + +static void do_stolen_accounting(void) +{ + struct vcpu_runstate_info state; + struct vcpu_runstate_info *snap; + u64 blocked, runnable, offline, stolen; + cputime_t ticks; + + get_runstate_snapshot(&state); + + WARN_ON(state.state != RUNSTATE_running); + + snap = &__get_cpu_var(runstate_snapshot); + + /* work out how much time the VCPU has not been runn*ing* */ + blocked = state.time[RUNSTATE_blocked] - snap->time[RUNSTATE_blocked]; + runnable = state.time[RUNSTATE_runnable] - snap->time[RUNSTATE_runnable]; + offline = state.time[RUNSTATE_offline] - snap->time[RUNSTATE_offline]; + + *snap = state; + + /* Add the appropriate number of ticks of stolen time, + including any left-overs from last time. Passing NULL to + account_steal_time accounts the time as stolen. */ + stolen = runnable + offline + __get_cpu_var(residual_stolen); + ticks = 0; + while(stolen >= NS_PER_TICK) { + ticks++; + stolen -= NS_PER_TICK; + } + __get_cpu_var(residual_stolen) = stolen; + account_steal_time(NULL, ticks); + + /* Add the appropriate number of ticks of blocked time, + including any left-overs from last time. Passing idle to + account_steal_time accounts the time as idle/wait. */ + blocked += __get_cpu_var(residual_blocked); + ticks = 0; + while(blocked >= NS_PER_TICK) { + ticks++; + blocked -= NS_PER_TICK; + } + __get_cpu_var(residual_blocked) = blocked; + account_steal_time(idle_task(smp_processor_id()), ticks); +} + + + +/* Get the CPU speed from Xen */ unsigned long xen_cpu_khz(void) { u64 cpu_khz = 1000000ULL << 32; @@ -338,6 +438,8 @@ static irqreturn_t xen_timer_interrupt(i ret = IRQ_HANDLED; } + do_stolen_accounting(); + return ret; } @@ -364,6 +466,8 @@ static void xen_setup_timer(int cpu) evt->irq = irq; clockevents_register_device(evt); + setup_runstate_info(); + put_cpu_var(xen_clock_events); } @@ -376,7 +480,7 @@ __init void xen_time_init(void) clocksource_register(&xen_clocksource); if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) { - /* Successfully turned off 100hz tick, so we have the + /* Successfully turned off 100Hz tick, so we have the vcpuop-based timer interface */ printk(KERN_DEBUG "Xen: using vcpuop timer interface\n"); xen_clockevent = &xen_vcpuop_clockevent; -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/