high frequency metrics collection and trace

[Jun Wang <junwang123@xxxxxxxxx>]

Folks,

In terms of the add-hoc high frequency
stats/metrics collection, do we have a known upper limit on the frequency to 
collect and display the metrics? Can we sample every 100 milliseconds or with 
even higher frequency? 

What about tracing with trace PMDA? How fast can an instrumented application 
push data through libpcp_trace? Is the PDU buffer size on the trace PMDA side 
configurable?  

Does the PMAPI have to use fetch/pull to collect data with certain fixed 
frequency? I assume that PMCD cannot push data to the monitoring side via 
PMAPI. 

However, for the trace PMDA case, does it make sense to collect multiple 
samples in the buffer, each with a different timestamp, and have the monitoring 
tools on the other side, such as pmchart, to  display multiple samples, per 
every fetch/pull, based on the timestamp? Just a thought on one option to 
increase the sample frequency without increasing the fetch/pull frequency. 

Thanks,
Jun