CODEWITHSUNDEEP
c++clinuxstack-memoryulimit
michael
michael

Reputation: 110660

Is there a limit of stack size of a process in linux

Is there a limit on the stack size of a process in Linux? Is it simply dependent on the RAM of the machine?

I want to know this in order to limit the depth of recursive calls to a function.

Upvotes: 21

Views: 21539

Answers (4)

AcidTonic
AcidTonic

Reputation: 196

Would have commented on the accepted answer but apparently I need more rep....

True Stack Overflow can be subtle and not always cause any error messages or warnings. I just had a situation where the only symptom was that socket connections would fail with strange SSL errors. Everything else worked fine. Threads could malloc(), grab locks, talk to the DB, etc. But new connections would fail at the SSL layer.

With stack traces from well within GnuTLS I was quite confused about the true cause. Nearly reported the traces to their team after spending lots of time trying to figure it out.

Eventually found that the stacksize was set to 8Mb and immediately upon raising it the problems vanished. Lowering the stack back to 8Mb brought the problem back (ABA).

So if you are troubleshooting what appears to be strange socket errors without any other warnings or uninitialized memory errors.... it could be stack overflow.

Upvotes: 1

MarkR
MarkR

Reputation: 63616

It largely depends what architecture you're on (32 or 64-bit) and whether you're multithreaded or not.

By default in a single threaded process, i.e. the main thread created by the OS at exec() time, your stack usually will grow until it hits something else in the address space. This means that it is generally possible, on a 32-bit machine, to have, say 1G of stack.

However, this is definitely NOT the case in a multithreaded 32-bit process. In multithreaded procesess, the stacks share address space and hence need to be allocated, so they typically get given a small amount of address space (e.g. 1M) so that many threads can be created without exhausting address space.

So in a multithreaded process, it's small and finite, in a single threaded one, it's basically until you hit something else in the address-space (which the default allocation mechanism tries to ensure doesn't happen too soon).

In a 64-bit machine, of course there is a lot more address space to play with.

In any case you can always run out of virtual memory, in which case you'll get a SIGBUS or SIGSEGV or something.

Upvotes: 5

caf
caf

Reputation: 239321

The stack is normally limited by a resource limit. You can see what the default settings are on your installation using ulimit -a:

stack size              (kbytes, -s) 8192

(this shows that mine is 8MB, which is huge).

If you remove or increase that limit, you still won't be able to use all the RAM in the machine for the stack - the stack grows downward from a point near the top of your process's address space, and at some point it will run into your code, heap or loaded libraries.

Upvotes: 36

Aryabhatta
Aryabhatta

Reputation:

The limit can be set by the admin.

See man ulimit.

There is probably a default which you cannot cross. If you have to worry about stack limits, I would say you need to rethink your design, perhaps write an iterative version?

Upvotes: 6

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