stacksize

Sorry, I don't have a solution in mind. Apple's technical documentation QA1419 appears to confirm the observed 64Meg limit on stacksize.

Dual 1.25 GHz G4 (among others) Mac OS X (10.3.9) Fink (obviously)

What about using the sysctl -w kern.sysv.shmmax command? Doesn't this command increase the shared memory size? If indeed the stack size limit is 64 Mb, that's a real serious limit since lots of scientific code require as much stack size as available RAM will permit. I know on HP-UX that when one increases the stack size, that the kernel is automatically rebuilt. Does Darwin have a similar function, beyond sysctl , to rebuild the kernel after changing stack size?


Ed

The shared memory limit doesn't have anything to do with it.

maxssiz, the kernel variable denoting the largest possible stack size, is set by the MAXSSIZ #define to 64MB at compile time for the PPC kernel.

We use -

LDFLAGS += -Wl,-stack_size -Wl,0x40000000 -Wl,-stack_addr -Wl,0xf0000000

to increase the stack size to 1GB. On tiger you can get more, but I have never needed it.

Interesting; I think Apple needs to update their docs. 😀

William,
Is MAXSSIZ a per thread limit? 64MB limits seems pretty small these days.

Sounds like Apple doesn't provide a mechanism for (knowledgeable) Users to change MAXSSIZ and re-build the kernel w/the new value via either the command line, or a GUI. Is this correct?


Ed

64M is the maximum size to which the system will auto-extend a process' stack; specifying a larger stack with -stack-size artificially extends that by creating a dedicated stack segment of a fixed size for the program.

It's possible a knowledgeable user could recompile Darwin after bumping up MAXSSIZ in /usr/include/ppc/vmparam.h, but obviously there are no promises as to whether that would work or not.