On September 4th, 2017, Salesforce experienced performance degradation on the following instances: EU2, EU4, EU6, EU7, EU9, EU11, CS83, CS84, CS85. The degradation started at 00:50 CEST and ended at 02:25 CEST. The total duration of the degradation was 1 hour and 35 minutes.
The performance is up and running again. To monitor the performance yourself, you can visit the Trust page provided by Salesforce.