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

From: MichaelDBA <MichaelDBA(at)sqlexec(dot)com>
To: frank picabia <fpicabia(at)gmail(dot)com>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: Error: "could not fork new process for connection: Cannot allocate memory"
Date: 2020-12-22 17:53:05
Message-ID: 95bf577e-f598-3ec5-0c2c-e2d1ca0d7f70@sqlexec.com
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perhaps kernel parameters under control of vmware: shmmax/shmall.

Regards,
Michael Vitale
>
> 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(at)sss(dot)pgh(dot)pa(dot)us
> <mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>> wrote:
>
> frank picabia <fpicabia(at)gmail(dot)com <mailto:fpicabia(at)gmail(dot)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
>

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