Commit 24fa33b3 authored by Mat's avatar Mat
Browse files

Add FAQ entry about segfaults with large arrays. 

A few people have reported segfaults with very large arrays. To my
great relief I eventually found out that this is not a bug in
SharedArray but rather an indication that the system ran out of POSIX
shared memory.
parent f95cb416

README.md

+19 −0
Original line number Diff line number Diff line
@@ -89,6 +89,25 @@ SharedArray uses the posix shm interface (`shm_open` and `shm_unlink`) 
and so should work on most operating systems that follow the posix

standards (Linux, *BSD, etc.).



FAQ

---



### On Linux, I get segfaults when working with very large arrays.



A few people have reported segfaults with very large arrays. To my

great relief I eventually found out that this is not a bug in

SharedArray but rather an indication that the system ran out of POSIX

shared memory. On Linux a `tmpfs` virtual filesystem is used to

provide POSIX shared memory, and by default it is given only about 20%

of the total available memory. That amount can be changed by

re-mounting the `tmpfs` filesystem with the `size` option:



	sudo mount -o remount,size=100% /run/shm



Also you can make the change permanent, on next boot, by setting

`SHM_SIZE=100%` in `/etc/defaults/tmpfs` on recent Debian/Devuan

installations.



Installation

------------