Horton

Re: Excessive PostmasterIsAlive calls slow down WAL redo

Andres Freund <andres@anarazel.de>

View thread View on postgr.es
From: Andres Freund <andres@anarazel.de>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Tom Lane <tgl@sss.pgh.pa.us>,Heikki Linnakangas <hlinnaka@iki.fi>,pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2018-04-10T01:34:31Z
Lists: pgsql-hackers 

On April 9, 2018 6:31:07 PM PDT, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>Andres Freund wrote:
>
>> Another approach, that's simpler to implement, is to simply have a
>> second selfpipe, just for WL_POSTMASTER_DEATH.
>
>Would it work to use this second pipe, to which each child writes a
>byte
>that postmaster never reads, and then rely on SIGPIPE when postmaster
>dies?  Then we never need to do a syscall.

I'm not following, could you expand on what you're suggesting?  Note that you do not get SIGPIPE for already buffered writes.  Which syscall can we avoid?

Andres
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

Commits

  1. Poll postmaster less frequently in recovery.

  2. Use signals for postmaster death on FreeBSD.

  3. Use signals for postmaster death on Linux.

  4. Introduce a pipe between postmaster and each backend, which can be used to