The Symptom
Users were experiencing a 5-15 second delay when saving a document to OneDrive or SharePoint, during which Word would show as “not responding”.
All machines in question use App Control for Business (WDAC).
The Cause
During the “not responding” period, Word is attempting to start the Web Client service, which is set to Manual.
svchost.exe launches, tries to load the WebClnt.dll library, but this is blocked by App Control for Business.
Word has to wait for this attempt to time out, before then giving up and saving anyway.
The Fix
Setting the Web Client service start type to Disabled prevents Word from attempting to start the service, fixing the delay.
The Diagnosis Process
Event Tracing for Windows and UIforETW strike again, along with the incredible utility of the public symbols for Office.
The process was similar to that which I documented here, where the process of saving comments in Word caused a hang. The key is to click Trace > Load Symbols to ensure we have function names in the trace.
Drilling down to the problem time area and then digging into the amount of time we spend in each function revealed that the time was being spent in davhlpr.dll!TriggerStartWebclientServiceIfNotRunning.
Well this does indeed sound like something to do with the Web Client service!
