Horton

Re: pgbench: could not connect to server: Resource temporarily unavailable

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Dunstan <andrew@dunslane.net>, Kevin McKibbin <kevinmckibbin123@gmail.com>, pgsql-performance@lists.postgresql.org
Date: 2022-08-24T04:53:33Z
Lists: pgsql-performance 
On Wed, Aug 24, 2022 at 3:06 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Thomas Munro <thomas.munro@gmail.com> writes:
> > Oh, one comment there is actually obsolete now AFAIK.  Unless there is
> > some reason to think personality(ADDR_NO_RANDOMIZE) might not work in
> > some case where sysctl -w kernel.randomize_va_space=0 will, I think we
> > can just remove that.
>
> AFAICS, f3e78069db7 silently does nothing on platforms lacking
> ADDR_NO_RANDOMIZE and PROC_ASLR_FORCE_DISABLE.  Are you asserting
> there are no such platforms?

That's a Linux-only sysctl.  ADDR_NO_RANDOMIZE is also Linux-only.
Both controls are old enough to be in any kernel that anyone's
developing on.  On further reflection, though, I guess the comment is
still useful.  ADDR_NO_RANDOMIZE only helps you with clusters launched
by pg_ctl and pg_regress.  A developer trying to run "postgres"
directly might still want to know about the sysctl, so I withdraw that
idea.

As for whether there are platforms where it does nothing: definitely.
These are highly OS-specific, and we've only tackled Linux and FreeBSD
(with other solutions for macOS and Windows elsewhere in the tree),
but I doubt it matters: these are just the OSes that have ASLR on by
default, that someone in our community uses as a daily driver to hack
PostgreSQL on, that has been annoyed enough to look up how to turn it
off :-)

Commits

  1. Doc: document possible need to raise kernel's somaxconn limit.

  2. Doc: prefer sysctl to /proc/sys in docs and comments.

  3. Remove our artificial PG_SOMAXCONN limit on listen queue length.

  4. Instead of believing SOMAXCONN from the system header files (which is