(In reply to Dragana Damjanovic [:dragana] from comment #1)
Can you look at this?
Can you give more information about MOZ_DISABLE_TASKCONTROLLER.
In old builds (more than 4 months ago), it used to change the code used to schedule main thread events. In theory this can result in very subtle timing differences. It also somewhat increases the overhead for runnables (although this is only really measurables for runnables that are no-ops, up to 50 000 runnables a second is fine).
I can't personally reproduce this on any machine I own.
The site above gives me 200 Mbps, which seems reasonable for a server in Tokyo.
Using speedtest.net I get 850 Mbps, which is somewhat below my internet connection capacity, although I get similar results from Edge. Our CPU usage does seem to be slightly higher than edge, nothing in the profile to obviously link this to differences in event handling though.
Profile Speedtest nightly here: https://share.firefox.dev/3dnRAQi
Here are some profiles with a build where the env var still worked:
Profile August build without env var set: https://share.firefox.dev/3s40iqS
Profile August build with env var set: https://share.firefox.dev/3u0JGT3
Nothing in here looks interesting to me, or different, then again, I can't reproduce any difference in the numbers either. No measurable impact from the TaskController is visible.