Messages in this thread | | | Date | Thu, 10 Dec 2009 18:57:37 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/4] ftrace - add function_duration tracer |
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* Frank Ch. Eigler <fche@redhat.com> wrote:
> Ingo Molnar <mingo@elte.hu> writes: > > > [...] > > Just off the top of my head we want to be able to trace: > > > > - max irq service latencies for a given IRQ > > - max block IO completion latencies for a app > > - max TLB flush latencies in the system > > - max sys_open() latencies in a task > > - max fork()/exit() latencies in a workload > > - max scheduling latencies on a given CPU > > - max page fault latencies > > - max wakeup latencies for a given task > > - max memory allocation latencies > > > > - ... and dozens and dozens of other things where there's a "start" > > and a "stop" event and where we want to measure the time between > > them. > > [...] > > FWIW, those who want to collect such measurements today can do so with > a few lines of systemtap script for each of the above.
Well, i dont think stap can do workload instrumentation. It can do system-wide (and user local / task local) - but can it do per task hierarchies?
Also, i dont think stap supports proper separation of per workload measurements either. I.e. can you write a script that will work properly even if multiple monitoring tools are running, each trying to measure latencies?
Also, i personally find built-in kernel functionality more trustable than dynamically built stap kernel modules that get inserted.
Ingo
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