Just commenting to say I'm also seeing this behaviour too. It doesn't seem to be the case when I first start the server, but every now and then I'm forced to close clients down and VcXsrv otherwise it just burns cpu time and drains my laptop battery :-/ At the point of closing all clients the server remains busy.
i965: Implement INTEL_performance_query backend
mesa: Separate INTEL_performance_query frontend
mesa: Model INTEL perf query backend after query obj BE
main/performance_query: s/GLboolean/bool/
mesa: Fix performance query id check
i965: extend query/counter structs for OA queries
i965: brw_context.h additions for OA unit query codegen