From: MichaelDBA <MichaelDBA@sqlexec.com>
To: frank picabia <fpicabia@gmail.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: Error: "could not fork new process for connection: Cannot allocate memory"
Date: Tue, 22 Dec 2020 12:53:05 -0500
Message-ID: <95bf577e-f598-3ec5-0c2c-e2d1ca0d7f70@sqlexec.com> (raw)
In-Reply-To: <CA+AKB6EZHm3=c_Lddgq+PMZozbmeYy61J751-FhkuJ5ZFj7oNQ@mail.gmail.com>
References: <CA+AKB6F6EGnLPFDqm1kcPtyeRWyY92vbfQk-3uFVbrERYu+PJg@mail.gmail.com>
<fce391ac5b00b86921e680ebd37eaa802e51dd39.camel@cybertec.at>
<492638.1608564438@sss.pgh.pa.us>
<CA+AKB6FUXcJH32YX9UYgV749NqBFMOh270moE7izBcZt+-VyJg@mail.gmail.com>
<CA+AKB6HxKgOvKAL8yuH7=Sc9ENs5Me4ouoGR16e9H3EdCWvKqg@mail.gmail.com>
<574264.1608600463@sss.pgh.pa.us>
<CA+AKB6EZHm3=c_Lddgq+PMZozbmeYy61J751-FhkuJ5ZFj7oNQ@mail.gmail.com>
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@sss.pgh.pa.us
> <mailto:tgl@sss.pgh.pa.us>> wrote:
>
> frank picabia <fpicabia@gmail.com <mailto: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
>
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To: pgsql-admin@postgresql.org
Cc: MichaelDBA@sqlexec.com, fpicabia@gmail.com
Subject: Re: Error: "could not fork new process for connection: Cannot allocate memory"
In-Reply-To: <95bf577e-f598-3ec5-0c2c-e2d1ca0d7f70@sqlexec.com>
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