Bill Burcham created GEODE-9002:
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Summary: Add Statistic for /proc/schedstat
Key: GEODE-9002
URL: https://issues.apache.org/jira/browse/GEODE-9002
Project: Geode
Issue Type: New Feature
Components: statistics
Reporter: Bill Burcham
Linux performance icon Brendan Gregg advocates the
[USE|http://www.brendangregg.com/usemethod.html] method of performance
analysis: Utilization Saturation and Errors.
When it comes to CPU, Geode captures a number of _utilization_ statistics. Some
are direct like LinuxSystemStats cpuIdle and cpuActive. Others are indirect
like:
But utilization statistics alone can't tell you when a resource (like CPU) is
_saturated_, i.e. when demand is higher than the servicing ability. If you're
just looking at utilization metrics, then a saturated system might look a lot
like a system just below saturation. In order to tell the difference,
saturation metrics are needed.
In the case of CPU, there is a conceptual queue in front of each processor.
Tasks (operating system threads) that are ready to run, enter a queue, and
after some delay, are given a time slice by an actual physical CPU.
You might think that Geode's LinuxSystemStats loadAverage1 and 5 and 15, might
fit this bill. Those statistics do provide some saturation information. The
problem is, they conflate CPU with I/O and other things (see [Linux Load
Averages: Solving the
Mystery|[http://www.brendangregg.com/blog/2017-08-08/linux-load-averages.html].)]
A better, more specific measure of CPU saturation is available through
statistics exposed via the /proc/schedstat virtual file.
When this ticket is complete, there will be a new statistic type called
LinuxThreadScheduler, with three associated statistics gathered directly from
/proc/schedstat or derived from data gathered from it:
* runningTimeNanos: sum of all time spent running by tasks on this processor
in nanoseconds
* queuedTimeNanos: sum of all time spent waiting to run by tasks on this
processor in nanoseconds
* tasksScheduledCount: # of tasks (not necessarily unique) given to the
processor
* meanTaskQueuedTimeNanos: average time that a ready-to-run task waited for a
CPU, since the last sample, in nanoseconds
One "statistic" will be gathered for each CPU. So a Geode process running on a
two-CPU system will capture two statistics, called "cpu0", "cpu1", each of this
new type.
By default Geode will not gather these new statistics. A TBD Java system
property will be used to enable gathering the new LinuxThreadScheduler
statistic.
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