Re: [SLAC #351542] caget crashing on psusr*

[Andrew Johnson <anj@aps.anl.gov>]

I would be happy to change the OSITHREAD_USE_DEFAULT_STACK setting for
64-bit CPUs because their virtual address space is big enough for
anything, but for 32-bit CPUs using the default stack size severely
limits the number of CA servers that a single client process can talk
to.  According to the CVS log Marty changed the default from YES to NO
in 2004, which may have been when we were trying to get the APS Gateway
to run on a Linux box.

On current Linux systems the default stack is typically 8-10MB per
thread, and the CA client library creates 2 threads per server, so it
needs 16-20MB of address space per server.  On 32-bit CPUs user-space
used to be limited to half of the virtual address space, i.e. 2GB =
2048MB, which should accommodate somewhere between 100 and 128 servers —
way too small for the APS and probably many other sites.

- Andrew
-- 
Optimization is the process of taking something that works and
replacing it with something that almost works, but costs less.
-- Roger Needham