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runtime libraries application on schedule()
- From: William Cohen <wcohen at redhat dot com>
- To: mhunt <mhunt at redhat dot com>
- Cc: SystemTAP <systemtap at sources dot redhat dot com>
- Date: Wed, 09 Mar 2005 17:39:54 -0500
- Subject: runtime libraries application on schedule()
Hi Martin,
I noticed that you checked in a bunch of runtime stuff today. I was
thinking about possible applications/instrumentations using the runtime
library. One of the things I was thinking was instrumentin the
schedule() function. It is called each time the processor yields. I
assume that many of the device drivers are written to yield the
processor when they are waiting for IO with a schedule.
Use a jprobe to instrument the entry to schedule().
Record the pid and the return address.
The information could be analyzed in a sevral different ways:
1) sum based on return address to find out which schedule points are
getting hit all the time
2) sum the counts by pid to figure out which pids are getting
rescheduled a lot
3) find out pid hitting which schedule() points
4) find out schedule() point being encountered by which process
Comments on implementing this instrumentation?
-Will