Re: WALWriteLocks

ok i have a small laptop with an even smaller vm :)

pgbench -i s 3
pgbench -c 20 -j 5 -T 900 -M prepared

select wait_event_type, wait_event from pg_stat_activity;

wait_event_type | wait_event
-----------------+---------------------
Activity | LogicalLauncherMain
Activity | AutoVacuumMain
LWLock | WALWrite
Lock | transactionid
Lock | tuple
LWLock | WALWrite
Lock | transactionid
Lock | transactionid
Lock | tuple
Lock | transactionid
Lock | transactionid
Lock | transactionid
Lock | tuple
IO | WALSync
Lock | transactionid
|
Activity | BgWriterHibernate
Activity | CheckpointerMain
LWLock | WALWrite

i then destroyed the slow WAL db
rm -rf data

and built a new one without additional latency to WALdir.

initdb -D data
pg_ctl -D data start

pgbench -i -s 3
pgbench -c 20 -j 5 -T 900 -M prepared

i see similar output as above
but no
WALWriteLock

old thread, just for reference. do not read into anything :)

PostgreSQL - hackers - An attempt to reduce WALWriteLock contention
(postgresql-archive.org)
<https://www.postgresql-archive.org/An-attempt-to-reduce-WALWriteLock-contention-td5935907.html>

Thanks,
Vijay

On Fri, 30 Apr 2021 at 00:22, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:

> On Fri, 2021-04-30 at 00:13 +0530, Vijaykumar Jain wrote:
> > I tried the below, but i could not simulate WALWriteLock waits.
> >
> > create table foo(id int)
> >
> > for i in {1..10}; do psql -c "begin transaction; insert into foo
> select 1 from generate_series(1, 1000); commit;" & done
>
> Perhaps you should do simple inserts of one row and run that script
> with a pgbench and lots of clients.
>
> Yours,
> Laurenz Albe
> --
> Cybertec | https://www.cybertec-postgresql.com
>
>