Hi Gregory,
On Thu, May 22, 2008 at 08:06:44AM -0600, Gregory Haskins wrote:
Nice tool! Helps in better visualization of the data in schedstats.
Using the tool, realized that most of the timing related stats therein
might not be completely usable in many scenarios, as might already be
known.
Without any additional load on the system, all the stats are nice and
sane. But, as soon as I ran my particular testcase, the data
pertaining to the delta of run_delay/cpu_time went haywire! I understand
that all the values are based on top of rq->clock, which relies on tsc that
is not synced across cpus and would result in skews/incorrect values.
But, turns out to be not so reliable data for debugging. This is
ofcourse nothing related to the tool, but for schedstat in
general...rather just adding on to the already existing woes with non-syned
tscs :-)
Maybe support for displaying process specific schedstat info might help?
We already do capture it under /proc/<pid>/schedstat. So, a -p switch for
pid maybe? Reason for this is when looking at the entire system stats, I
might not be able to get lot of information specific to my particular
application...like when a particular thread suffers a lot of delay
waiting for the runqueue... just a thought!
--
Regards,
Ankita Garg (ankita@in.ibm.com)
Linux Technology Center
IBM India Systems & Technology Labs,
Bangalore, India
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