Ever since updating to v1.8.0 on Windows, I’ve been seeing Syncthing suddenly starting to use 25% CPU (i.e. 1 core) more or less continuously, while performing lots of network I/O. Resource monitor shows the syncthing.exe constantly sending and receiving 22-23 kB/s for no apparent reason.
This does not happen immediately after starting the application. It usually remains quiet for a while, but once it starts, it just keeps going. The other Syncthing peers are 6 Android devices running v1.7.1.
The funny thing is, it doesn’t seem to be doing anything in the logs. But I started up Wireshark and there seems to be continuous UDP traffic with the other Syncthing peers – I’ve attached an example.
On upgrade all indexes are exchanged. That shouldn’t take long in general, but could be the culprit. Would be detectable by remote devices not being up-to-date.
Here’s a snippit of the log after enabling connection logging. I also did another capture of 5000 packets. Lots of constant UDP traffic to the other Syncthing peers. It’s now been a few days since the upgrade to v1.8.0 on my Windows PC and this is still happening, so this doesn’t seem normal.
Here’s a slightly longer log with connection logging enabled. I’m afraid I don’t know what would be interesting, though. There seem to be a lot of reconnects, but I think that’s probably normal with the Android devices, esp. on a mixed IPv6/IPv4 network.
I don’t think it’s index exchanging either. The remote devices all appear to be synchronised.
Nothing suspicious there. It just seems to be reconnecting. I guess you should start by trying yo upgrade the other side to the same version, and if that doesn’t help, see if what happens if you disable quic.