Is anyone using the schedgraph.d script?

[Adrian Chadd]

On 26 January 2015 at 19:01, Ryan Stone <rysto32 at gmail.com> wrote:
> Hm, there was one bug in that script.  I uploaded a fixed version.  The fix was:
>
> -       printf("%d %d KTRGRAPH group:\"thread\", id:\"%s/%s tid %d\",
> state:\"runq add\", attributes: prio:%d, linkedto:\"%s/%s tid %d\"\n",
> cpu, timestamp, args[0]->td_proc->p_comm, args[0]->td_name,
> args[0]->td_tid, args[0]->td_priority, curthread->td_proc->p_comm,
> curthread->td_name, args[0]->td_tid);
> +       printf("%d %d KTRGRAPH group:\"thread\", id:\"%s/%s tid %d\",
> state:\"runq add\", attributes: prio:%d, linkedto:\"%s/%s tid %d\"\n",
> cpu, timestamp, args[0]->td_proc->p_comm, args[0]->td_name,
> args[0]->td_tid, args[0]->td_priority, curthread->td_proc->p_comm,
> curthread->td_name, curthread->td_tid);
>
> Note that the last printf argument used args[0] instead of curthread
> as intended.

Cool! Thanks!

> One other thing that I have noticed with the schedgraph data gathering
> is that unlike KTR, in dtrace every CPU gathers its data into a
> CPU-local buffer.  This can mean that a CPU that sees a large number
> of scheduler events will roll over its ring buffer much more quickly
> than a lightly loaded CPU.  This can lead to a confusing or misleading
> schedgraph output at the beginning of the time period.  You can
> mitigate this problem by allowing dtrace to allocate a larger ring
> buffer with:
>
> #pragma D option bufsize=32m
>
> (You can potentially tune it even higher than that, but that's a good
> place to start)
>
>
> Finally, I've noticed that schedgraph seems to have problems
> auto-detecting the clock frequency, so I tend to forcifully specify
> 1GHz (dtrace always outputs time in units of ns, so this is always
> correct to do with dtrace-gather data)

Good to know.

Is there any reason why this isn't just checked into -HEAD and -10?



-adrian