Il 28/06/2013 04:57, Marcelo Tosatti ha scritto:
>
> One possibility for a softlockup report in a Linux VM, is that the host
> system is overcommitted to the point where the watchdog task is unable
> to make progress (unable to touch the watchdog).
>
> Maintain the increment in stolen time for the period of
> softlockup threshold detection (20 seconds by the default),
> and report this increment in the softlockup message.
>
> Overcommitment is then indicated by a large stolen time increment,
> accounting for more than, or for a significant percentage of the
> softlockup threshold.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
>
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 05039e3..ed09d58 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -34,6 +34,8 @@ int __read_mostly watchdog_thresh = 10;
> static int __read_mostly watchdog_disabled;
> static u64 __read_mostly sample_period;
>
> +#define SOFT_INTRS_PER_PERIOD 5
> +
> static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
> static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
> static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
> @@ -127,9 +129,51 @@ static void set_sample_period(void)
> * and hard thresholds) to increment before the
> * hardlockup detector generates a warning
> */
> - sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
> + sample_period = get_softlockup_thresh() *
> + ((u64)NSEC_PER_SEC / SOFT_INTRS_PER_PERIOD);
> }
>
> +#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
> +struct steal_clock_record {
> + u64 prev_stolen_time;
> + u64 stolen_time[SOFT_INTRS_PER_PERIOD];
> + int idx;
> +};
> +
> +static DEFINE_PER_CPU(struct steal_clock_record, steal_record);
> +static void record_steal_time(void)
> +{
> + struct steal_clock_record *r;
> + int cpu = smp_processor_id();
> + u64 steal_time;
> + r = &per_cpu(steal_record, cpu);
> +
> + steal_time = paravirt_steal_clock(cpu);
> + r->stolen_time[r->idx] = steal_time - r->prev_stolen_time;
> + r->idx++;
> + if (r->idx == SOFT_INTRS_PER_PERIOD)
> + r->idx = 0;
> + r->prev_stolen_time = steal_time;
> +}
> +
> +static unsigned int get_accumulated_steal(int cpu)
> +{
> + int idx;
> + u64 t = 0;
> + struct steal_clock_record *r = &per_cpu(steal_record, cpu);
> +
> + for (idx = 0; idx < SOFT_INTRS_PER_PERIOD; idx++)
> + t += r->stolen_time[idx];
> +
> + do_div(t, 1000000);
> +
> + return t;
> +}
> +
> +#else
> +static void record_steal_time(void) { return; }
> +#endif
> +
> /* Commands for resetting the watchdog */
> static void __touch_watchdog(void)
> {
> @@ -271,6 +315,9 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
> /* kick the hardlockup detector */
> watchdog_interrupt_count();
>
> + /* record steal time */
> + record_steal_time();
> +
> /* kick the softlockup detector */
> wake_up_process(__this_cpu_read(softlockup_watchdog));
>
> @@ -316,6 +363,10 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
> printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
> smp_processor_id(), duration,
> current->comm, task_pid_nr(current));
> +#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
> + printk(KERN_EMERG "soft lockup stolen time = %ums\n",
> + get_accumulated_steal(smp_processor_id()));
Perhaps print this only if nonzero (so that it doesn't print it on bare
metal)? Then you can remove the #ifdef too, it will be optimized away
by the compiler for !CONFIG_PARAVIRT_TIME_ACCOUNTING.
Paolo
> +#endif
> print_modules();
> print_irqtrace_events(current);
> if (regs)
>
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