Unusually high CPU usage during Watch Together playback?

[bl4ckswordsman]

I've noticed in v1.24.1 (might've started before) that CPU usage on my Linux machine is way higher than it used to be during Watch Together playback, as my fans start spinning now (as opposed to earlier versions when they didn't spin at all).

I see that there's been some tweaks made by the dev to Watch Together lately but I can't pinpoint what it was exactly.
And I'm not sure whether logs would make this more clear.

[edde746]

Does it only happen when using watch together or normal playback too?

[bl4ckswordsman]

I tried with normal playback and the CPU usage was lower than during Watch Together playback

[edde746]

@bl4ckswordsman

• Is the higher CPU usage on the host, the guest, or both?
• Roughly how much CPU does Plezy use during normal playback vs Watch Together with the same media?
• Is the usage constantly high, or does it spike every few seconds?

If you can, please also enable debug logging, reproduce a short Watch Together session with the same media, then go to Settings > Logs and upload/share the log ID here. That should make it easier for me to see whether it’s repeatedly doing sync/seek corrections during WT playback.

[bl4ckswordsman]

• Is the higher CPU usage on the host, the guest, or both?

I think it's higher only for the host (the guest hasn't noticed any difference lately). The guest is running Android TV so it's not as straightforward to monitor live CPU usage.

• Roughly how much CPU does Plezy use during normal playback vs Watch Together with the same media?
  I ran some quick tests with pidstat and these are these results:

Plezy — Normal Playback

	%usr	%system	%wait	%CPU
Average	27.97%	4.43%	0.16%	32.41%

Plezy — Watch Together

	%usr	%system	%wait	%CPU
Average	42.57%	6.46%	0.16%	49.03%
Delta in % points	+14.6%	+2.0%	0.0%	+16.6%
Delta in %	+52.2%	+45.8%	0.0%	+51.3%

Clarification: %usr -> App-level CPU (UI, decoding); %system -> Kernel CPU on app's behalf; %wait -> Waiting for CPU time; %CPU -> Total usage

• Is the usage constantly high, or does it spike every few seconds?

From what I've noticed, there are some seemingly regular high CPU spikes (which is what I initially noticed as well).

If you can, please also enable debug logging, reproduce a short Watch Together session with the same media, then go to Settings > Logs and upload/share the log ID here. That should make it easier for me to see whether it’s repeatedly doing sync/seek corrections during WT playback.

I enabled debug mode and this is a snippet of some logs during Watch Together playback:

WT debug logs

Besides MPV INFO logs, there's just the ping logs:

[21:13:34.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:31.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:30.975] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:13:30.975] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:13:28.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:25.957] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:13:25.957] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:13:25.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:22.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:20.971] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:13:20.971] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:13:19.214] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:16.212] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:15.967] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:13:15.967] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:13:13.211] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:10.966] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:13:10.966] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:13:10.208] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:07.205] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:05.961] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:13:05.961] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:13:04.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:01.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:13:00.995] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:13:00.994] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:58.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:55.962] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:55.962] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:55.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:52.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:50.984] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:50.984] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:49.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:46.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:45.979] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:45.979] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:43.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:40.976] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:40.976] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:40.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:37.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:35.972] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:35.972] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:34.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:31.215] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:30.970] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:30.970] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:28.212] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:25.982] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:25.982] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:25.207] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:22.204] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:21.013] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:21.013] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:19.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:16.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:15.972] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:15.972] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:13.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:10.959] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:10.959] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:10.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:07.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:05.981] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:05.981] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:12:04.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:01.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:12:00.971] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:12:00.971] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:11:58.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:55.970] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:11:55.970] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:11:55.214] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:52.212] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:50.966] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:11:50.965] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:11:49.208] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:46.204] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:45.967] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:11:45.967] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:11:43.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:40.972] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:11:40.972] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:11:40.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:37.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:35.993] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:11:35.993] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:11:34.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:31.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:31.067] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]
[21:11:31.067] [DEBUG] WatchTogether: Received SyncMessageType.ping from b08e[REDACTED]
[21:11:28.202] [DEBUG] WatchTogether: Broadcasting SyncMessageType.positionSync to 1 peers
[21:11:25.983] [DEBUG] WatchTogether: Sending SyncMessageType.pong to b08e[REDACTED]

[edde746]

I included a Watch Together CPU-overhead reduction in the latest release (1.25.0), so this may already be improved.

Could you try 1.25.0 and compare normal playback vs Watch Together again with the same media?

If it still happens, please share:

• updated CPU numbers
• whether the spikes still look periodic
• a short debug log snippet from 1.25.0

[bl4ckswordsman]

• I tried both 1.25.0 and 1.26.0 and they show slightly lower CPU usage numbers. WT in 1.26.0 used about 8% less than WT in 1.24.1 (from 49% to 45%).
• From what I can see, the CPU usage is more even now, can't notice any major spikes.
• There's only unrelated MPV logs, even with DEBUG logs on.

This might not impact many users so if I can pinpoint it better I'll open an issue.

Thank you for your effort in building Plezy!