POSIX version of epicsThreadCreate needs to enable code calling pthread_attr_setstacksize

[Jeff Hill]

> Andrew wrote:
> Divide that remaining 2GB by the stack space allocated for
> each thread and you'll get an estimate of the maximum
> number of threads that you can run in a single process.
>
> In our case (Red Hat), the default stacksize is 10240
> Kbytes per thread, which gives a limit of 204 threads.
>
> # Limit stacksize for Linux to increase number of threads
> # 10240 is 204 threads (default)
> # 4096 is 512 threads
> ulimit -s 4096

Some comments:

o I had to read this a 2nd time to see that this is 4096 KBytes (not Bytes) per thread.
o this is virtual, and not actual space used in the page file
o the actual space used by each thread is probably two to three orders of magnitude smaller

> Dirk wrote:
> That means, that CA is not scalable any more (?)
>

Contrary to my previous concerns, it appears that a 64 bit Linux system will *not* be required for large gateways, and that CA scales just fine if one changes the "ulimit -s" quota. This fits with our experience with vxWorks where IOCs are routinely used with more than 200 circuits (within 32 MByte non-virtual address spaces).

Its starting to appear that the root problem is that the posix version of epicsThreadCreate needs to call pthread_attr_setstacksize to do the equivalent of "ulimit -s". I looked in the code and this is turned off if OSITHREAD_USE_DEFAULT_STACK is defined, and I see "-D OSITHREAD_USE_DEFAULT_STACK" on the Linux compiler's command line.

Original Mantis Bug: mantis-143
    http://www.aps.anl.gov/epics/mantis/view_bug_page.php?f_id=143

[Jeff Hill (johill-lanl)]

An update on the results from epicsMaxThreadsHost on windows:

o On W2K the maximum is always 2000 threads.
o On WXP the maximum is 30,000 if STACK_SIZE_PARAM_IS_A_RESERVATION is specified when spawning the thread, and 2000 otherwise.

I will be changing the windows version of epicsThreadCreate to use STACK_SIZE_PARAM_IS_A_RESERVATION.

[mrk (mrk-aps)]

fixed R3.14.7

[Andrew Johnson (anj)]

R3.14.7 Released