MacOS seems to be slowing down FFS when it's in the background

[abstractrealism]

I think I've maybe noticed this for a while but just now had an extreme case that's prompting me to post. I was Cmd-Tabbing between two apps and noticed the completion badge on FFS was at 90% or so and was surprised it hadn't finished as I'd started it a long time ago. When I switched to it to see what was going on it said 7m30s remaining. The transfer speed quickly sped up as I watched and it ended up finishing in maybe 30-45s. I am attaching a screenshot of the completion graphs. You'll notice the speed starts off strong, then at a certain point abruptly slows. There are a few spots where it resumes the initial, faster speed, including just before the end, when I switched to it. So it seems like it's being de-prioritized when not in focus. I'm not sure if this is entirely up to MacOS, and nothing to be done about it, or not?
The particulars of my sync: Syncing with Google Drive, threads set to 4 I believe, 8 files were copying up, 1 down. All were at least a few hundred MB, the one copying down (I believe that's the one that was copying last, still in progress during the time in question) was around 8GB. Total being 14GB. I have a 500/500 connection, so I'd expect it to finish in maybe 10m tops, being conservative, definitely not over 40.
MacOS Sonoma 14.5, FFS was on 13.7, I just upgraded to 13.9 but didn't see anything that looked related in the release notes, but apologies if I missed it.

[Zenju]

I suspect macOS "App Nap" might be responsible for the slow performance. Can you try the following beta and see if this fixes this issue: https://www.mediafire.com/file_premium/lymj08uqqzt0ubz/FreeFileSync_13.10_macOS_beta.zip

[abstractrealism]

Downloading it now and I'll give it a try! I don't think it happens every time so it may take a while to confirm it's fixed. I'm not familiar with that feature but just from the name it sounds like exactly what I guessed might be happening so I bet you're right!

[abstractrealism]

@Zenju, unfortunately in that beta version within a few seconds of clicking "Compare" the app crashes. I've saved the crash report, I can attach that here if you like. Just wanted to confirm there's no personal information in there or anything? Don't have time to thoroughly examine at the moment.

[Zenju]

Sorry, fixed: https://www.mediafire.com/file/y3epe05yas8gl74/FreeFileSync_13.10_macOS_beta%25282%2529.zip

[abstractrealism]

No worries at all, I really appreciate you looking into this so quickly! This build is working, but running pretty slowly. The sync is bouncing between ~500KB/s to 1.5MB/s with occasional spikes to 2MB/s. Looking at the screenshot I posted earlier, looks like that one finished at 5.7MB/s so a fair bit slower. Don't believe anything should have changed on my network. Just ran a speedtest and it looks normal.

[abstractrealism]

Apologies, maybe something was indeed going on with my network, it sped up a lot after a while, around the 20m mark it suddenly sped up to about 50 MB/s! False alarm I guess, sorry about that!