Re: PGSQL 11.4: shared_buffers and /dev/shm size

> I think it could fail that way for two reasons: /dev/shm size limit
> (mount option, which I think you are saying you have set to 4GB?), or
> your system ran out of RAM +swap.

df /dev/shm
Filesystem 1K-blocks Used Available Use% Mounted on
shm 4194304 351176 3843128 9% /dev/shm

mount | grep /dev/shm
shm on /dev/shm type tmpfs (rw,nosuid,nodev,noexec,relatime,size=4194304k)

I have no swap and 8GB of RAM, when there is no active queries only ~800MB of RAM is used. So I don't believe that it is out of memory problem.

> The directly listing in your first
> message only shows 1.4GB, not 4GB, so perhaps it's the second problem.

I cannot catch the right moment with ls, but I've run bash for-loop that that logs "df /dev/shm" every minute and the last entry before fail shows that 89% of /dev/shm is used:

Filesystem 1K-blocks Used Available Use% Mounted on
shm 4194304 3732368 461936 89% /dev/shm

There is no other processes that use /dev/shm.

> It's strange that it's hashing the ~20B row table instead of the ~30M row table.

It could be a question for another mail thread =)

Konstantin