Horton

Re: Use pg_pwritev_with_retry() instead of write() in dir_open_for_write() to avoid partial writes?

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Nathan Bossart <nathandbossart@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-03-06T04:29:50Z
Lists: pgsql-hackers 
On Mon, Feb 20, 2023 at 01:54:00PM +0530, Bharath Rupireddy wrote:
> I ran some tests on my dev system [1] and I don't see much difference
> between v3 and v4. So, +1 for v3 patch (+ argument order swap) from
> Andres to keep the code simple and elegant.

This thread has stalled for a couple of weeks, so I have gone back to
it.  Testing on a tmpfs I am not seeing a difference if performance
for any of the approaches discussed.  At the end, as I am the one
behind the introduction of pg_pwrite_zeros(), I have applied v3 after 
switches the size and offset parameters to be the same way as in v4.
--
Michael

Commits

  1. Revise pg_pwrite_zeros()

  2. Use pg_pwrite_zeros() in walmethods.c

  3. Introduce pg_pwrite_zeros() in fileutils.c

  4. Move pg_pwritev_with_retry() to src/common/file_utils.c

  5. Restore pg_pread and friends.

  6. Remove dead pread and pwrite replacement code.