UploadChecksumWorker hammering CPU

Gitlab has been very slow recently with high CPU usage. Busy Background Jobs always shows two UploadChecksumWorker jobs running, and the sidekiq log shows hundreds of them running per minute, for example:

2017-08-07_15:01:56.27448 2017-08-07T15:01:56.274Z 5547 TID-ow2fhculw UploadChecksumWorker JID-ab9acb02dd57d4c399a04067 INFO: start
2017-08-07_15:01:56.27668 2017-08-07T15:01:56.276Z 5547 TID-ow2fhcwns UploadChecksumWorker JID-ab03788b0d449544e6ffa4e1 INFO: done: 1.345 sec
2017-08-07_15:01:57.32791 2017-08-07T15:01:57.327Z 5547 TID-ow2fhcvso UploadChecksumWorker JID-6ba88249bb66db413eb11cd0 INFO: start
2017-08-07_15:01:57.33992 2017-08-07T15:01:57.339Z 5547 TID-ow2fhctrc UploadChecksumWorker JID-ec2799e7a0905da5576bf427 INFO: done: 1.073 sec
2017-08-07_15:01:57.70612 2017-08-07T15:01:57.705Z 5547 TID-ow2fhctl8 UploadChecksumWorker JID-62bcd67cd114664515caf5cc INFO: start
2017-08-07_15:01:57.71242 2017-08-07T15:01:57.712Z 5547 TID-ow2fhculw UploadChecksumWorker JID-ab9acb02dd57d4c399a04067 INFO: done: 1.438 sec
2017-08-07_15:01:58.29894 2017-08-07T15:01:58.298Z 5547 TID-ow2fhcufs UploadChecksumWorker JID-f0625743134f869cae9c3d2d INFO: start
2017-08-07_15:01:58.31299 2017-08-07T15:01:58.312Z 5547 TID-ow2fhcvso UploadChecksumWorker JID-6ba88249bb66db413eb11cd0 INFO: done: 0.985 sec
2017-08-07_15:01:59.13292 2017-08-07T15:01:59.132Z 5547 TID-ow2fhcvac UploadChecksumWorker JID-d861b8f189246028623935c1 INFO: start
2017-08-07_15:01:59.19860 2017-08-07T15:01:59.198Z 5547 TID-ow2fhcufs UploadChecksumWorker JID-f0625743134f869cae9c3d2d INFO: done: 0.9 sec

Is this normal? If I stop the processes they come back within a few seconds, and they come back if I restart the application. Is this what is slowing down Gitlab, and if so, how can I stop it?

Thanks!

I have the same problem here.
BTW, my ‘uploads’ directory is on cifs.
After rebooting, the CPU usage is low now. At least for now.