Re: task time tapset

[Josh Stone <jistone at redhat dot com>]

On 10/09/2009 08:17 AM, Mark Wielaard wrote:
> Hi,
>
> As an addition to the proc_mem tapset I created a task_time tapset. Like
> the process memory tapset it only works on the current task. But that
> makes it really trivial to implement. I think it would be a nice
> addition since it allows you to do these "pass based statistics" fully
> dynamically (and they would of course also work with function probes, or
> any other probe that targets user processes).

Looks good to me.

Since this doesn't operate on arbitrary tasks, I wonder if it would make 
sense to drop the "task_" prefix, like the functions in context.stp. 
Maybe time_string() sounds too generic though... just thinking aloud...

> These are total user and system times. It doesn't include real time atm.
> In theory this can be gotten. The task struct keeps the start time. But
> this is in monotonic or boot time and we currently only have daytime. It
> shouldn't be too hard to add that, but I didn't want to do that atm.
> Recent kernels export a per cpu_clock() (based on sched_clock) that
> might be helpful.

Yes please!  I don't think real time is that critical here, but I think 
that this clock source would be very useful in general.  Most uses now 
of gettimeofday are just to measure time elapsed, and a monotonic clock 
is much more appropriate for that.  It can fall back on gettimeofday for 
older kernels.

Josh