For our benchmarks it looks like we've hard coded requesting 5000 calls per
completion queue:
https://github.com/grpc/grpc/blob/master/test/cpp/qps/server_async.cc.
And I think we target 3 threads per completion queue to manage contention.
I'd hazard that 5000 was roughly the smallest number for t
How can I explicitly debug the size of the completion queue? I tried with
`export GRPC_TRACE=pending_tags` and there were always pending tags as I
fill the queue with the RPC that I'm benchmarking and another one which is
unsued. I've also tried with replicating the rpc on the same queue multipl
