Horton

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

Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>

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From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
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: 2023-02-20T08:24:00Z
Lists: pgsql-hackers 
On Mon, Feb 20, 2023 at 11:03 AM Michael Paquier <michael@paquier.xyz> wrote:
>
> > I'm inclined to go with my version, with the argument order swapped to
> > Bharath's order.
>
> Okay.  That's fine by me.

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.

[1]
HEAD: 16MB (12.231 ms), 8190 Bytes (0.199 ms), 8192 Bytes (0.176 ms),
1GB (603.668 ms), 10GB (21184.936 ms (00:21.185))
v3 patch: 16MB (12.632 ms), 8190 Bytes (0.183 ms), 8192 Bytes (0.166
ms), 1GB (610.428 ms), 10GB (22647.308 ms (00:22.647))
v4 patch: 16MB (12.044 ms), 8190 Bytes (0.167 ms), 8192 Bytes (0.139
ms), 1GB (603.848 ms), 10GB (21225.331 ms (00:21.225))

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

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.