DOM M1 slowdowns with 1 host and 2 encode servers

[briancallahan]

Hello all!

I’ve been using DOM for the last few years, through several version iterations. Last year, I experimented with adding a M1 Mac Mini to my set up as an encode server, and noticed a pretty good speed up using the (at the time) alpha version supporting M1. At a few points I tried adding random encode servers in various combos to speed up long jobs (an Intel i5 MBP, a new M1 MacBook Air, an iMac 5k i7), but casually noticed that it seemed to be optimal with one host and one encode server. Because I was in production, I didn’t take the time to do any real tests, but now I have a different setup and I’m doing some testing to work this out.

Now, I have a M1 Pro MacBook Pro, networked via Ethernet to two M1 Mac Minis (same baseline 8MB ram and cpu spec).

I’m Using the newest version 2.16.5 of both the main application and encode server (I downloaded and installed today, but this is also the first day I’ve tested this new setup, so I don’t have previous version data).

I’m using as a test a 4.5 minute 1920x1080 25fps film, in a flat container, with stereo audio (no audio conversions, except for gain adjustment).

These are the times I’m getting for various combinations:

M1 Pro MBP Host only: 7:20 minutes (avg 15.3fps)
Host + single M1 Mac Mini encode server: 6:01 (avg 18.7fps)
Host + two M1 Mac Mini encode servers: 7:32 (avg 14.9fps)

It seems like my casual observation last year holds true. I’m getting the best speeds with The host plus one encode server. When I add a second, it’s even slower than the host alone.

Everything is default set up (10 threads for 10 cores on M1 Pro MBP and 8 threads each on the M1 Mac Minis, all plugged into a gigabit switch with short Cat5e cables.

Any thoughts on why I might be seeing this, or where the bottleneck likely is with 3 computers vs 2? Or am I just testing all wrong?

Cheers and thanks for the help!

Brian

[carl]

Hi Brian

That is an interesting result! It sounds like there's a bug somewhere...

As a first step it would be great if you could attach (or email to carl@dcpomatic.com ) the "log" file from the project you made on the host. That might give some clues as to what is going on.

[briancallahan]

Well, this really makes me feel like a novice... how do I access the log? I've been looking in the interface, but can't quite make out how to view the log. I'm sure it's very obvious...

[carl]

Sorry - it's not especially obvious!

When you made a project on your "master" computer you specified a folder for the project; if you look in that folder, there should be a file just called "log" - that file could be useful in working out what happened.

[briancallahan]

Hey Carl,

I’m just checking in to make sure you got all the files I emailed you (sometime in March, but then I’ll went out of town and forgot to follow up). I don’t expect you’d have any resolution on the issue yet, but just wanted to make sure you had what you needed from me, and check if any other tests on my end would be helpful.

Cheers!

Brian

[carl]

I've just merged a hopeful fix for this bug, so it would be worth trying out 2.16.21 when it's available on the test download page - hopefully within the next day or two.

[carl]

I just uploaded 2.16.21.