Re: Need help identifying a periodic performance issue.

On Tue, Nov 16, 2021 at 04:43:25AM +0000, Robert Creager wrote:
> We’re executing the following copy to fill a table with approximately 5k records, then repeating for a total of 250k records. Normally, this copy executes < 1 second, with the entire set taking a couple of minutes. The problem is not reproducible on command, but usually within a couple of hours of starting some test runs.
>
> COPY ds3.blob (byte_offset, checksum, checksum_type, id, length, object_id) FROM STDIN WITH DELIMITER AS ‘|’
>
> But, occasionally we get into a huge performance bottleneck for about 2 hours, where these copy operations are taking 140 seconds or so
>
> Nov 15 22:25:49 sm4u-34 postgres[5799]: [381-1] db=tapesystem,user=Administrator,app=PostgreSQL JDBC Driver,client=127.0.0.1 LOG: duration: 145326.293 ms statement: COPY ds3.blob (byte_offset, checksum, checksum_type, id, length, object_id) FROM STDIN WITH DELIMITER AS '|'

> I’m logging statements with pgbadger monitoring the logs. There are no apparent auto-vacuum’s running, nor any vacuums, nor anything at all really. Other select queries around that time frame are executing normally.

What about checkpoints ?

Would you show the "^checkpoint starting" and "^checkpoint complete" logs
surrounding a slow COPY ?

> We’re coming from PostgreSQL 9.6 on FreeBSD 11 where we did not see this problem, but have a major release upgrade happening. I’m checking to see if this machine was updated or was a fresh install.
> PostgreSQL 13.2 on amd64-portbld-freebsd13.0, compiled by FreeBSD clang version 11.0.1 (git(at)github(dot)com<mailto:git(at)github(dot)com>:llvm/llvm-project.git llvmorg-11.0.1-0-g43ff75f2c3fe), 64-bit
>
> Changes made to the settings in the postgresql.conf file
> checkpoint_timeout | 30min | configuration file
> log_checkpoints | on | configuration file
> log_lock_waits | on | configuration file
...
> shared_buffers | 21679MB | configuration file

> Operating system and version:
> FreeBSD sm4u-34 13.0-STABLE FreeBSD 13.0-STABLE #0: Mon Sep 13 10:11:57 MDT 2021

> These are the system calls made over 30 seconds from Postgres during a slowdown.
...
> fsync 27

--
Justin