Performance issues

We have instrumented the "nwsip.pl" script to evaluate the performance of the NWS server.

The timing of each NWS query has been recorded in a log, using the gettimeofday Unix system call. Its accuracy largely exceeds the measured intervals.

Several experiments have been run in NWS installation at CNAF:

In summary:

• delays are significantly different for "nws_extract" (that return measures) and "nws_search" (that search the registry of NWS processes) queries;
• nws_search queries took, in our setting, a time ranging around 20 msecs;

  

• nws_extract queries took a significantly higher time, ranging around 100 msecs;

  

  

  

Although one might expected that "nws_extract" take a longer time (since it requires the access to a memory server, that in our case is located on the sensor), it is nonetheless difficult to justify a difference of one order of magnitude.

Hypotheses:

• the access to the data is extremely expensive;
• the computation and the selection of the best forecast is extremely expensive.

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