Re: pg_upgrade failing for 200+ million Large Objects

On Fri, 2024-03-15 at 19:18 -0400, Tom Lane wrote:
> This patch seems to have stalled out again. In hopes of getting it
> over the finish line, I've done a bit more work to address the two
> loose ends I felt were probably essential to deal with:

Applies and builds fine.

I didn't scrutinize the code, but I gave it a spin on a database with
15 million (small) large objects. I tried pg_upgrade --link with and
without the patch on a debug build with the default configuration.

Without the patch:

Runtime: 74.5 minutes
Memory usage: ~7GB
Disk usage: an extra 5GB dump file + log file during the dump

With the patch:

Runtime: 70 minutes
Memory usage: ~1GB
Disk usage: an extra 0.5GB during the dump

Memory usage stayed stable once it reached its peak, so no noticeable
memory leaks.

The reduced memory usage is great. I was surprised by the difference
in disk usage: the lion's share is the dump file, and that got substantially
smaller. But also the log file shrank considerably, because not every
individual large object gets logged.

I had a look at "perf top", and the profile looked pretty similar in
both cases.

The patch is a clear improvement.

Yours,
Laurenz Albe