Re: Error: "could not fork new process for connection: Cannot allocate memory"

Thanks for the responses. 

We'll take this up with VMware support and then if it isn't a configuration issue, move it along to Redhat Linux support.

It was also useful to learn cgroups default support within the kernel can use up so much memory on a system with larger RAM.  On the next reboot this will free up about 1.6 GB RAM.  It might help with a little wiggle room until we know more about the other issue which seems to limit us to 1/2 our RAM.

On Mon, Dec 21, 2020 at 9:27 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

frank picabia <fpicabia@gmail.com> writes:
> My VMware admin has come back with a graph showing memory use over
> the period in question.  He has looked over other indicators
> and there are no alarms triggered on the system.
> It jives with what Cacti reported.  Memory was never exhausted
> and used only 50% of allocated RAM at the most.

> If it's not a configuration issue in Postgres, and both internal and
> external tools
> show memory was not consumed to the point of firing off the "cannot fork"
> error, would that mean that there is a bug in either the kernel or Postgres?

[ shrug... ]  Postgres is just reporting to you that the kernel wouldn't
perform a fork().  Since you've gone to great lengths to show that
Postgres isn't consuming excessive resources, either this is a kernel bug
or you're running into some kernel-level (not Postgres) allocation limit.
I continue to suspect the latter.  Desultory googling shows that VMware
can be configured to enforce resource allocation limits, so maybe you
should be taking a hard look at your VMware settings.

                        regards, tom lane