Re: pg_dump 3 times as slow after 8.4 -> 9.5 upgrade

Hi Tom

I'm honestly not sure about anything. =) I use the exact same flags as with 8.4 for the dump:

${BINARY_PATH}/pg_dump --host=localhost --user=postgres --no-password --blobs --format=custom --verbose --file=${pg_dump_filename}_${database}.backup ${database}

So unless the default behaviour have changed in 9.x I'd say I don't use compression. I will try to force it to no compression and see if it's different.

Sadly the instruments session stopped recording when I logged out of the system yesterday. Doh. =/

Cheers

--
Henrik Cednert
cto | compositor

Filmlance International
mobile [ + 46 (0)704 71 89 54 ]
skype [ cednert ]

On 21 Nov 2017, at 22:01, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us<mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>> wrote:

"Henrik Cednert (Filmlance)" <henrik(dot)cednert(at)filmlance(dot)se<mailto:henrik(dot)cednert(at)filmlance(dot)se>> writes:
I'm not sure if I can attach screenshots here. Trying, screenshot from instruments after running for a few mins.

It looks like practically all of pg_dump's time is going into deflate(),
ie zlib. I don't find that terribly surprising in itself, but it offers
no explanation for why you'd see a slowdown --- zlib isn't even our
code, nor has it been under active development for a long time, so
presumably 8.4 and 9.5 would have used the same version. Perhaps you
were doing the 8.4 dump without compression enabled?

regards, tom lane