epicsSnPrintf is very slow when converting string arrays in GDD's aitConvert.cc

["Jeff Hill" <johill@lanl.gov>]

All,

 

I have discovered that a PCAS hang can occur when clients are fetching very large arrays as strings. Just to convert the number of elements that fit in a very large EPICS_CA_MAX_ARRAY_SIZE buffer with epicsSnPrintf can take a very long time. It appears that this required about 33 seconds during testing with EPICS_CA_MAX_ARRAY_SIZE of 10,000,000. Based on that I calculate 33 / ( 10,000,000 / MAX_STRING_SIZE ) is 0.000132 seconds per conversion. Is epicsSnPrintf() really that slow?

 

The solution appears to be to use the cvtFast library where it is in range in GDD’s aitConvert.cc. The cvtFast functions are a bit scary in today’s world - because a buffer size isn’t passed in – BTW. The current workaround is to just not use them for buffer sizes below some threshold.

 

Jeff
______________________________________________________
Jeffrey O. Hill           Email        johill@lanl.gov
LANL MS H820              Voice        505 665 1831
Los Alamos NM 87545 USA   FAX          505 665 5107

 

Message content: TSPA