[lttng-dev] [PATCH lttng-modules 1/5] fix: timer/trace: Improve timer tracing (v5.2)

[Mathieu Desnoyers]

All merged into lttng-modules master, 2.11, 2.10, 2.9 branches.

I updated the field names for patch 4/5 as discussed.

Thanks,

Mathieu

----- On May 21, 2019, at 4:33 PM, Michael Jeanson mjeanson at efficios.com wrote:

> See upstream commit:
> 
>  commit f28d3d5346e97e60c81f933ac89ccf015430e5cf
>  Author: Anna-Maria Gleixner <anna-maria at linutronix.de>
>  Date:   Thu Mar 21 13:09:21 2019 +0100
> 
>    timer/trace: Improve timer tracing
> 
>    Timers are added to the timer wheel off by one. This is required in
>    case a timer is queued directly before incrementing jiffies to prevent
>    early timer expiry.
> 
>    When reading a timer trace and relying only on the expiry time of the timer
>    in the timer_start trace point and on the now in the timer_expiry_entry
>    trace point, it seems that the timer fires late. With the current
>    timer_expiry_entry trace point information only now=jiffies is printed but
>    not the value of base->clk. This makes it impossible to draw a conclusion
>    to the index of base->clk and makes it impossible to examine timer problems
>    without additional trace points.
> 
>    Therefore add the base->clk value to the timer_expire_entry trace
>    point, to be able to calculate the index the timer base is located at
>    during collecting expired timers.
> 
> Signed-off-by: Michael Jeanson <mjeanson at efficios.com>
> ---
> instrumentation/events/lttng-module/timer.h | 22 +++++++++++++++++++++
> 1 file changed, 22 insertions(+)
> 
> diff --git a/instrumentation/events/lttng-module/timer.h
> b/instrumentation/events/lttng-module/timer.h
> index 8703ea0..997084f 100644
> --- a/instrumentation/events/lttng-module/timer.h
> +++ b/instrumentation/events/lttng-module/timer.h
> @@ -89,6 +89,27 @@ LTTNG_TRACEPOINT_EVENT(timer_start,
> )
> #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,2,0)) */
> 
> +#if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,2,0))
> +/**
> + * timer_expire_entry - called immediately before the timer callback
> + * @timer:	pointer to struct timer_list
> + *
> + * Allows to determine the timer latency.
> + */
> +LTTNG_TRACEPOINT_EVENT(timer_expire_entry,
> +
> +	TP_PROTO(struct timer_list *timer, unsigned long baseclk),
> +
> +	TP_ARGS(timer, baseclk),
> +
> +	TP_FIELDS(
> +		ctf_integer_hex(void *, timer, timer)
> +		ctf_integer(unsigned long, now, jiffies)
> +		ctf_integer_hex(void *, function, timer->function)
> +		ctf_integer(unsigned long, baseclk, baseclk)
> +	)
> +)
> +#else
> /**
>  * timer_expire_entry - called immediately before the timer callback
>  * @timer:	pointer to struct timer_list
> @@ -107,6 +128,7 @@ LTTNG_TRACEPOINT_EVENT(timer_expire_entry,
> 		ctf_integer_hex(void *, function, timer->function)
> 	)
> )
> +#endif
> 
> /**
>  * timer_expire_exit - called immediately after the timer callback returns
> --
> 2.17.1

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com