Re: Show WAL write and fsync stats in pg_stat_io

Hi,

On Tue, 31 Oct 2023 at 16:57, Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com> wrote:
> On Thu, 26 Oct 2023 at 09:28, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> >
> > And perhaps just putting that everything that calls
> > pgstat_count_io_op_time() under track_io_timing is just natural?
> > What's the performance regression you would expect if both WAL and
> > block I/O are controlled by that, still one would expect only one of
> > them?
>
> I will check these and I hope I will come back with something meaningful.

I applied the patches on upstream postgres and then run pgbench for each
available clock sources couple of times:
# Set fsync = off and track_io_timing = on
# pgbench -i -s 100 test
# pgbench -M prepared -c16 -j8 -f <( echo "SELECT
pg_logical_emit_message(true, \:client_id::text, '1234567890');") -T60 test

Results are:

╔═════════╦═══════════════════════════════╦════════╗
║ ║ track_wal_io_timing ║ ║
╠═════════╬═══════════════╦═══════════════╬════════╣
║ clock ║ on ║ off ║ change ║
║ sources ║ ║ ║ ║
╠═════════╬═══════════════╬═══════════════╬════════╣
║ tsc ║ ║ ║ ║
║ ║ 514814.459170 ║ 519826.284139 ║ %1 ║
╠═════════╬═══════════════╬═══════════════╬════════╣
║ hpet ║ ║ ║ ║
║ ║ 132116.272121 ║ 141820.548447 ║ %7 ║
╠═════════╬═══════════════╬═══════════════╬════════╣
║ acpi_pm ║ ║ ║ ║
║ ║ 394793.092255 ║ 403723.874719 ║ %2 ║
╚═════════╩═══════════════╩═══════════════╩════════╝

Regards,
Nazir Bilal Yavuz
Microsoft