Horton

Re: make MaxBackends available in _PG_init

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Nathan Bossart <nathandbossart@gmail.com>, "Bossart, Nathan" <bossartn@amazon.com>, Fujii Masao <masao.fujii@oss.nttdata.com>, "wangsh.fnst@fujitsu.com" <wangsh.fnst@fujitsu.com>, Andres Freund <andres@anarazel.de>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Greg Sabino Mullane <htamfids@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2022-02-09T03:57:37Z
Lists: pgsql-hackers 
On Tue, Feb 8, 2022 at 9:38 PM Michael Paquier <michael@paquier.xyz> wrote:
> On Tue, Feb 08, 2022 at 04:12:26PM -0500, Robert Haas wrote:
> > After some investigation I've determined that it's no longer Friday
> > afternoon. I also spent time investigating whether the patch had
> > problems that would make me uncomfortable with the idea of committing
> > it, and I did not find any. So, I committed it.
>
> @@ -1641,8 +1642,8 @@ SignalBackends(void)
>          * XXX in principle these pallocs could fail, which would be bad. Maybe
>          * preallocate the arrays?  They're not that large, though.
>          */
> -       pids = (int32 *) palloc(MaxBackends * sizeof(int32));
> -       ids = (BackendId *) palloc(MaxBackends * sizeof(BackendId));
> +       pids = (int32 *) palloc(GetMaxBackends() * sizeof(int32));
> +       ids = (BackendId *) palloc(GetMaxBackends() * sizeof(BackendId));
>
> You could have optimized this one, while on it, as well as the ones in
> pgstat_beinit() and pg_safe_snapshot_blocking_pids().  It is not hot,
> but you did that for all the other callers of GetMaxBackends().  Just
> saying..

Well I didn't do anything myself except review and commit Nathan's
patch, so I suppose you mean he could have done that, but fair enough.
I don't mind if you want to change it around.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

Commits

  1. Add a new shmem_request_hook hook.

  2. Remove non-functional code for unloading loadable modules.

  3. Fix misleading comments about background worker registration.

  4. Revert the addition of GetMaxBackends() and related stuff.

  5. Fix typo in multixact.c

  6. Reduce more the number of calls to GetMaxBackends()

  7. Remove MaxBackends variable in favor of GetMaxBackends() function.

  8. Fix comments about bgworker registration before MaxBackends initialization

  9. Fix bogus assertion in BootstrapModeMain().

  10. Make sure MaxBackends is always set