A recent change to Soulseek.NET began invoking event handlers asynchronously, and this change means that uploads from a remote user are no longer processed one by one. This sped things up considerably, but slskd can get overwhelmed when someone enqueues a bunch of files at once.

To help ensure the application remains responsive while processing big batches of uploads, cap the number of concurrent upload processes at 10.

It might make sense to cap this to 10 per user, but I'm not sure that will actually give the stability we want. 10 regardless of user will do that, while risking creating a bottleneck.