Re: Estimating HugePages Requirements?

On Wed, Mar 23, 2022 at 7:25 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Tue, Mar 15, 2022 at 03:44:39PM -0700, Nathan Bossart wrote:
> > A simple approach could be to just set log_min_messages to PANIC before
> > exiting. I've attached a patch for this. With this patch, we'll still see
> > a FATAL if we try to use 'postgres -C' for a runtime-computed GUC on a
> > running server, and there will be no extra output as long as the user sets
> > log_min_messages to INFO or higher (i.e., not a DEBUG* value). For
> > comparison, 'postgres -C' for a non-runtime-computed GUC does not emit
> > extra output as long as the user sets log_min_messages to DEBUG2 or higher.
>
> > puts(config_val ? config_val : "");
> > +
> > + /* don't emit shutdown messages */
> > + SetConfigOption("log_min_messages", "PANIC", PGC_INTERNAL, PGC_S_OVERRIDE);
> > +
> > ExitPostmaster(0);
>
> That's fancy, but I don't like that much. And this would not protect
> either against any messages generated before this code path, either,

But neither would the suggestion of redirecting stderr to /dev/null.
In fact, doing the redirect it will *also* throw away any FATAL that
happens. In fact, using the 2>/dev/null method, we *also* remove the
message that says there's another postmaster running in this
directory, which is strictly worse than the override of
log_min_messages.

That said, the redirect can be removed without recompiling postgres,
so it is probably still hte better choice as a temporary workaround.
But we should really look into getting a better solution in place once
we start on 16.

> My solution for the docs is perhaps too confusing for the end-user,
> and we are talking about a Linux-only thing here anyway. So, at the
> end, I am tempted to just add the "2> /dev/null" as suggested upthread
> by Nathan and call it a day. Does that sound fine?

What would be a linux only thing?

--
Magnus Hagander
Me: https://www.hagander.net/
Work: https://www.redpill-linpro.com/