CODEWITHSUNDEEP
clinux
Roman Byshko
Roman Byshko

Reputation: 9032

Why is stack size almost always 132KiB on a Linux machine?

The following command computes size of the stack for each running process on a Linux machine.

# find /proc -maxdepth 1 -type d -regex '/proc/[0-9]*' -exec cat '{}'/maps \; | grep stack | cut -d' ' -f1 | gawk --non-decimal-data 'BEGIN{FS="-"} {printf "%d\n", (("0x" $2) - ("0x" $1))/1024}' | sort

In almost all the cases size of the stack is 132KiB. Why is this number so special? Is this the minimum possible size of the stack?

Upvotes: 3

Views: 477

Answers (1)

caf
caf

Reputation: 239251

The kernel sets new process stacks to 128kB in setup_arg_pages():

stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */

When you add a single 4kB guard page, that comes to 132kB. If the process has never used more than this much stack, it won't have been expanded past this size.

Upvotes: 5

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