add concurrency example

www/docs/concurrency.md

@@ -0,0 +1,54 @@
+---
+id: concurrenct
+title: Concurrency Options
+---
+
+This is a walkthrough of different concurrency options available to control the number of concurrent workers that `ghz` utilizes to make requests to the server. All examples are done using a simple unary gRPC call.
+
+Many of these options are similar to the load control options, but independently control the concurrent workers utilized.
+
+## Step Up Concurrency
+
+```
+ghz --insecure --async --proto /protos/helloworld.proto \
+  --call helloworld.Greeter/SayHello \
+  -n 10000 --rps 200 \
+  --concurrency-schedule=step --concurrency-start=5 --concurrency-step=5 --concurrency-end=50 --concurrency-step-duration=5s \
+  -d '{"name":"{{.WorkerID}}"}' 0.0.0.0:50051
+
+Summary:
+  Count:	10000
+  Total:	50.05 s
+  Slowest:	52.04 ms
+  Fastest:	50.19 ms
+  Average:	50.59 ms
+  Requests/sec:	199.79
+
+Response time histogram:
+  50.187 [1]	|
+  50.373 [1786]	|∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
+  50.558 [3032]	|∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
+  50.743 [2822]	|∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
+  50.929 [1536]	|∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
+  51.114 [562]	|∎∎∎∎∎∎∎
+  51.299 [194]	|∎∎∎
+  51.485 [42]	|∎
+  51.670 [15]	|
+  51.855 [6]	|
+  52.041 [4]	|
+
+Latency distribution:
+  10 % in 50.33 ms
+  25 % in 50.42 ms
+  50 % in 50.57 ms
+  75 % in 50.73 ms
+  90 % in 50.89 ms
+  95 % in 51.01 ms
+  99 % in 51.24 ms
+
+Status code distribution:
+```
+
+This test performs a constant load at `200` RPS, starting with `5` workers, and increasing concurrency by `5` workers every `5s` until we have `50` workers. At that point all `50` workers will be used to sustain the constant `200` RPS until `10000` total request limit is reached. Worker count over time would look something like:
+
+![Constant Load](images/step_up_c_const_rps_wc.svg)