Shared Memory Structure?

[ben5192]

I am storing things in a shared memory zone allocated with
ngx_shared_memory_add and allocating each slab with ngx_slab_alloc_locked
(as these items don’t need to be locked particularly). The problem I'm
having is that I add the shared memory with exactly the amount I need.
However, the final large thing to be allocated fails, but after this a lot
more smaller things are also allocated without any problem. There is enough
space for it but it has a problem with a large chunk when space is getting
tight.
Does anyone know why this is or how to fix it? My guess was that nginx
structures the shared memory in a way that means there is enough memory
(which I have made sure there is) but it is not continuous.
Thanks.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,266569,266569#msg-266569