Messages in this thread |  | | | Date | Thu, 10 Dec 2009 13:04:12 -0500 | | From | "Frank Ch. Eigler" <> | | Subject | Re: [PATCH 2/4] ftrace - add function_duration tracer |
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Hi -
> > 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?
It can track the evolution of task hierarchies by listening to process forking events, and filter other kernel/user events according to then-current hierarchy data. One primitive implementation of this is in the target_set.stp tapset, but it's easy to script up other policies.
> 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?
Sure, always has. You can run many scripts concurrently, each with its own internal state. (Overheads accumulate, sadly & naturally.)
> Also, i personally find built-in kernel functionality more trustable > than dynamically built stap kernel modules that get inserted.
I understand. In the absence of a suitable bytecode engine in the kernel, this was the only practical way to do everything we needed.
- FChE
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