Syncthing-Fork v2 uses far too much battery over v1

Support Android
42

Just to be clear, the old version (1.29.6) works on my Pixel 6a with Android 16 with no excessive battery usage whatsoever. This is not a general Pixel/Android battery drain issue, it is definitely something that changed in the latest syncthing (quite possibly in conjunction with Pixel/Android 16).

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43

Actually, just maintaining the connection (e.g. to the discovery server, relays, and other devices) can drain a lot of battery, especially if you’re moving around on a mobile network. I think the main issue is if there is battery drain from the app when Syncthing proper isn’t even running (e.g. because it’s set to work only on Wi-Fi or when charging).

44

Pixel 6 with latest Android 16 here too, started looking after battery life got cut in half and ended up here. Managed to get the logs for syncthing-fork and syncthing itself, but they don’t show anything repeating endlessly etc. App has an SELinux denied message:

20:01:58W/libsyncthingnat type=1400 audit(0.0:7128): avc: denied { read } …

Syncthing has multiple “Failed to acquire open port“ warnings. I’ll gladly post the logs here, if anyone could confirm I’d not be leaking secrets. Thanks all for looking into this.

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45

This message has been there for years, also on v1.

46

I don’t know if I understood correctly but I have no battery problems, as long as syncthing is not active. When Wi-Fi is off (only syncing on Wi-Fi) and syncthing does nothing, battery consumption goes back to normal again.

47

A bit late to the party, but did you already try to limit the connection count back to 1? This should mimic the v1 behaviour on the network layer.

1 Like
48

Yep.

There is even battery drain without configuring anything (see m11kaa’s post #11) …

49

Well if Syncthing drains battery, it’s either caused by CPU usage and/or IO. As it also happens without anything configured and even without the wrapper being involved(termux), this would narrow it down to some housekeeping stuff. We have something like that for the sqlite database but it should be a NOOP most of the time and even more so if the database is virtually empty.

50

I ran syncthing through Termux (fresh config) for a few hours and will attach the generated support bundle. (I think this should only “leak” my public IP, which is acceptable to me :sweat_smile: ). These files don’t mean too much to me right now, but hopefully others will be able to spot irregularities faster. Unfortunately, I did not notice as much of a battery drain, but that is fairly hard to say for sure.

support-bundle-LD2BOGR-2025-10-19T152901.zip (44.0 KB)

2 Likes
51

Ok, I also have this issue

  1. Pixel 7 Android 16
    1. Phone was working great with syncthing fork 1.x
    2. I have set to automatically upgrade with github
    3. At some point github updated to 2.0, battery issues started
      1. High battery consumption on idle without pending uploads or any device connected. On Android Battery: Sometimes 30% sometimes more. Sometimes less but more often super high
    4. Wasted time trying configuration changes
    5. Downgraded to 1.x by using google play version - all issues resolved
      1. On idle consumption is consistently less than 1%
    6. I posted issue on github and my posted was deleted
  2. Pixel 9 Pro on Android 16 (upgraded my phone in late Sep)
    1. At some point google play updated to 2.x and I didn’t notice, battery issues started
      1. High battery consumption on idle without pending uploads or any device connected. On Android Battery: Sometimes 30% sometimes more. Sometimes less but more often super high
    2. Wasted time trying configuration changes
    3. Nothing worked, including removing other devices and fiddling with settings
    4. Very accidentally realized the phone was not on 2.x. Downgraded via sideload - ALL ISSUES RESOLVED
      1. On idle consumption is consistently less than 1% most times it does not even show

It is a bit unfortunate that my post (and some others) are remove from github

Sadly I won’t be doing any upgrades for the time being until good results are shown

Syncthing rocks - really hopping this is addressed

3 Likes
52

Has anyone news on this topic? How could we get better information on the issue? Would it help to file a bug report?

53

Please provide feedback on a fresh setup with one test folder using the latest release/rc. Until now, no one did react to it in this topic.

54

I’d like to see how things change with the upcoming release that includes the fix of @marbens

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55

which fix exactly?

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56
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57

To be clear, the root cause of this battery problem is still unknown and this fix was not created with this problem in mind. But @akirapink’s comment

does kinda point at one of the issues that was in mind when creating that fix.

58

Folder scanning already has abysmal performance on Android if things are working as intended (thanks Google). I wouldn’t be surprised that this would take its toll on the battery if performance degrades further.

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59

Alright, this is what I did now:

  1. Installed Syncthing-Fork v2.0.10.2 (fresh setup) on Pixel 6, Android 16 QPDR1 and enabled verbose logging.
  2. Started syncthing 2.0.10-1 (Arch Linux, up-to-date) on my desktop with a fresh config as well.
  3. Shared a folder (from my desktop to my phone), containing an empty text file and a wallpaper picture.

The battery usage went up again (watched Youtube for the better part of an hour just to compare, but syncthing’s battery usage was comparable, even though nothing changed in the folder). I’ll attach the log files.

android.log (2.8 KB)

syncthing.log (94.3 KB)

Please let me know if you need anything else!

3 Likes
60

Here is another case of excessive battery usage since upgrading to v2.

I have a Pixel 8 with Android 16 and it is clearly related to Syncthing running. I was on a week of vacation the other day and intentionally did not connect to any WiFi during this time (Syncthing is limited to running only when connected to WiFi) and I would get over 2+ days with my battery.

When I am at home and phone is connected to WiFi all day and thus Syncthing is running all day I hardly get over one just a single day.