Re: Multiple full page writes in a single checkpoint?

On Wed, Feb  3, 2021 at 08:07:16PM -0500, Bruce Momjian wrote:
> > > I can try to add a hint-bit-page-write page counter, but that might
> > > overflow, and then we will need a way to change the LSN anyway.
> > 
> > That's just a question of width...
> 
> Yeah, the hint bit counter is just delaying the inevitable, plus it
> changes the page format, which I am trying to avoid.  Also, I need this
> dummy record only if the page is marked clean, meaning a write
> to the file system already happened in the current checkpoint --- should
> not be to bad.

In looking your comments on Sawada-san's POC patch for buffer
encryption:

    https://www.postgresql.org/message-id/20210112193431.2edcz776qjen7kao%40alap3.anarazel.de

I see that he put a similar function call in exactly the same place I
did, but you pointed out that he was inserting into WAL while holding a
buffer lock.

I restructured my patch to not make that same mistake, and modified it
for non-permanent buffers --- attached.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee