Experimental Physics and
Industrial Control System

It appears that the 3 EPICS stack sizes if we don't use defaults
are 128K, 256K, and 512K.    There's a lot of room between
these and the typical 8-10MB linux default.   Why so small for
these stack sizes, which are only used for posix systems?

- Bruce

On 12/12/2011 05:47 PM, Andrew Johnson wrote:

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

References:

RE: [SLAC #351542] caget crashing on psusr* Jeff Hill

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

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

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