Re: PVXS and CA Put benchmark

[Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov>]

On 4/22/26 7:30 PM, Bernardo Brotas Carvalho via Tech-talk wrote:

Hi Epics tech-talkers,

While working on a prototype gateway to a WinCCOA  I ended up using PVXS C++ client library,

but I was a little surprised by the relatively low Throughput (when compared to a plain CA client), 

when making a bunch of "puts" to 1000 ai-PVs, served by a softIocPVX.

A couple of thoughts.

Overall put_pvxs.cpp is structured correctly, so the PUTs are being issued in parallel.

After exec()ing all Operations, you could call client::Context::hurryUp() [1].  Somewhat analogous to ca_flush_io(), this optional hint can speed up the search phase.  If you want to understand the effect, you can set:

export PVXS_LOG=pvxs.client.setup=DEBUG

Look for messages mentioning "hurryUp()" [2].

Also, you and your friend might wish to read about std::condition_variable or epicsEvent instead of sleep_for() in a loop ;)

[1] https ://epics-base.github.io/pvxs/client.html#_CPPv4N4pvxs6client7Context7hurryUpEv

[2] https ://github.com/epics-base/pvxs/blob/3d854e492c44261ca25541dfda2177e934efb8b7/src/client.cpp#L723-L731

My first result, made on a 10 year old Intel PC where:

## PVXS Client

=== EPICS PVXS Put Benchmark: 1000 PVs ===

…

=== SUMMARY ===

  Client creation:       1.02404 ms (0.100708%)

  Put issue phase:       4.97025 ms (0.488793%)

  Wait phase:            1010.81 ms (99.4072%)

  ---------------------------------

  TOTAL TIME:            1016.84 ms

  Throughput:            983.437 puts/sec

## CA Client

=== EPICS CA Put Benchmark: 1000 PVs ===

…. 

=== SUMMARY ===

  Connect phase:         100.629 ms (95.7%)

  Put issue phase:       0.195 ms (0.2%)

  Wait phase:            4.252 ms (4.0%)

  ---------------------------------

  TOTAL TIME:            105.130 ms

  Throughput:            9512.0 puts/sec

A second test, performed on an more recent 40-core Intel(R) Xeon(R) CPU, and using PV grouping, pool, threading, etc. 

( 50 groups of ~20 PVs each), gave me ~2000 puts/sec for PVXS , but still far from CA.

My Env is:

EPICS_CA_ADDR_LIST=localhost

EPICS_CA_AUTO_ADDR_LIST=NO

EPICS_PVA_ADDR_LIST=localhost

EPICS_PVA_AUTO_ADDR_LIST=NO

EPICS_PVA_NAME_SERVERS=localhost

Am I missing something?

In case of interest, my codes made “With a Little Help From My AI Friends”, are in:

https://gitlab.com/ifmif-dones1/winccoa-epics/-/tree/pvxs/epics/pvxs/epics_benchmark

Thanks in advance

Bernardo

IPFN-IST Portugal