Hi all,
I noticed something weird: Basically, manually copying a file into my DCIM/Camera folder on my phone results in a much faster sync to my laptop than if I take a photo with the camera app, which also places the picture into DCIM/Camera. (I made sure that the test files which I manually copied into DCIM/Camera are always new, i.e. syncthing has not seen/hashed them before.)
I tested this on a Pixel 8 and also a Pixel 5. On both phones, I tested this with the stock Camera app from GrapheneOS and OpenCamera from F-Droid.
My general setup
- Linux laptop running syncthing 1.29.3
- In advanced syncthing settings, set
fsWatcherDelaySto0.5.
- In advanced syncthing settings, set
- Phone (Pixel 8) with GrapheneOS (currently Android 15) running syncthing-fork 1.29.4 (from F-Droid)
- In advanced syncthing settings, set
fsWatcherDelaySto1.
- In advanced syncthing settings, set
- Phone (Pixel 5) with GrapheneOS (currently Android 14) running syncthing-fork 1.29.4 (from F-Droid)
- In advanced syncthing settings, set
fsWatcherDelaySto1.
- In advanced syncthing settings, set
- Syncthing only runs over LAN via local discovery (no global discovery, no NAT, no relaying).
- Each phone has their
DCIMfolder shared with the laptop, so no loops in the sync graph.
For the following, by “full folder” I mean a folder that contains 800 photos (3.8 GB) and 200 videos (8.3 GB), so a total of 1000 files (12.1 GB). By “empty folder”, I mean a folder that contains about 10 photos à 5 MB.
I did use the same dataset of photos and videos for both phones, for consistency.
Measurements on Pixel 8
- New photo with Stock Camera into “full folder”:
45s-48s - New photo with OpenCamera into “full folder”:
15s - New photo with Stock Camera into “empty folder”:
1s - New photo with OpenCamera into “empty folder”:
1s - Manually copy a file into “full folder”:
1s - Manually copy a file into “empty folder”:
1s
Measurements on Pixel 5
- New photo with Stock Camera into “full folder”:
4s - New photo with OpenCamera into “full folder”:
5s - New photo with Stock Camera into “empty folder”:
1s - New photo with OpenCamera into “empty folder”:
1s - Manually copy a file into “full folder”:
1s - Manually copy a file into “empty folder”:
1s
Additional info
I measured the time just by looking at the clock, while having something like watch -n .1 'ls -lat pixel8_DCIM_sync/Camera | head -n 10' running on my laptop. I did several measurements, on different days, and rebooted the phone inbetween.
On all cases where the time was above 1 second, there was a temporary syncthing file present, e.g. .syncthing.IMG_20250505_001914_896.jpg.tmp, which was then renamed to e.g. IMG_20250505_001914_896.jpg when the sync finished (that’s when I noted the time).
I’m aware of syncthing’s slow performance on folders that contain many files, but it seems that this issue here is different.
My question
I would be interested if someone could think of an explanation of this issue? And maybe even has ideas for a fix, or how one could debug this further? Maybe someone could try to reproduce this on another phone?
Semi-related: Over the course of these tests, I renamed DCIM/Camera to DCIM/OpenCamera and DCIM/OpenCamera to DCIM/Camera (using one temporary name to avoid a collision). After that, I had to restart syncthing-fork for it to recognize new photos again, for some reason (even though I did a manual rescan and waited until both devices were in sync again).
Thank you 