Re: Re: BUG #13685: Archiving while idle every archive_timeout with wal_level hot_standby

On Wed, Feb 24, 2016 at 2:40 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> This has the merit to be clear, thanks for the input. Whatever the
> approach taken at the end we have two candidates:
> - Extend XLogInsert() with an extra argument for flags (Andres)
> - Introduce XLogInsertExtended with this extra argument and let
> XLogInsert() in peace (Robert and I).
> Actually, I lied, there was still something I could do for this
> thread: attached are two patches implementing both approaches as
> respectively a-1 and a-2. Patch b is the set of logs I used for the
> tests to show with a low checkpoint_timeout that checkpoints are
> getting correctly skipped on an idle system.
>
> Let's see what happens next.

FWIW, I just made a couple of 5-min pgbench runs on my laptop (scale
100, 24 clients using 4 threads) with checkpoint_timeout = 30s and a
small value of shared_buffers to minimize the work of each checkpoint,
and I am seeing similar spikes with variations that can be assimilated
to noise. See for example the graph attached. Trying to put more
contention on the extra locks taken before entering the checkpoint
section to scan the progress LSN looks kind of difficult :) But that's
not really a surprise.
--
Michael