one more doc

Author: Tofel

book/src/SUMMARY.md

@@ -77,6 +77,7 @@
       - [Custom Loki metrics](./libs/wasp/benchspy/loki_custom.md)
       - [Standard Prometheus metrics](./libs/wasp/benchspy/prometheus_std.md)
       - [Custom Prometheus metrics](./libs/wasp/benchspy/prometheus_custom.md)
+      - [To Loki or not to Loki?](./libs/wasp/benchspy/loki_dillema.md)
       - [Reports](./libs/wasp/benchspy/reports/overview.md)
         - [Standard Report](./libs/wasp/benchspy/reports/standard_report.md)
           - [Adding new QueryExecutor](./libs/wasp/benchspy/reports/new_executor.md)

book/src/libs/wasp/benchspy/loki_dillema.md

@@ -0,0 +1,15 @@
+# BenchSpy - To Loki or not to Loki?
+
+You might be asking yourself whether you should use `Loki` or `Generator` query executor if all you
+need are basic latency metrics.
+
+As a rule of thumb, if all you need is a single number that describes the median latency or error rate
+and you are not interested in directly comparing time series, minimum or maximum values or any kinds
+of more advanced calculation on raw data, then you should go with the `Generator`.
+
+Why?
+
+Because it returns a single value for each of standard metrics using the same raw data that Loki would use
+(it accesses the data stored in the `WASP`'s generator that would later be pushed to Loki).
+This way you can run your load test without a Loki instance and save yourself the need of calculating the
+median and 95th percentile latency or the error ratio.

book/src/libs/wasp/benchspy/overview.md

@@ -1,15 +1,15 @@
 # BenchSpy
 
 BenchSpy (short for benchmark spy) is a WASP-coupled tool that allows for easy comparison of various performance metrics.
-It supports three types of data sources:
-* `Loki`
-* `Prometheus`
-* `WASP generators`
 
-And can be easily extended to support additional ones.
-
-Since it's main goal is comparison of performance between various releases or versions of applications (for example, to catch performance degradation)
-it is `Git`-aware and is able to automatically find the latest relevant performance report.
+It's main characteristics are:
+* three built-in data sources:
+    * `Loki`
+    * `Prometheus`
+    * `WASP generator`
+* standard/pre-defined metrics for each data source
+* ease of extensibility with custom metrics
+* ability to load latest performance report based on Git history
 
 It doesn't come with any comparation logic, other than making sure that performance reports are comparable (e.g. they mesure the same metrics in the same way),
 leaving total freedom to the user.

book/src/libs/wasp/benchspy/simplest_metrics.md

@@ -49,6 +49,6 @@ compareValues(string(benchspy.ErrorRate), 1.0)
 
 And that's it! You have written your first test that uses `WASP` to generate the load and `BenchSpy` to make sure that neither median latency nor 95th latency percentile
 nor error rate has changed significantly between the runs. You did that without even needing a Loki instance, but what if you wanted to leverage the power
-of LogQL? We will look at that in the [next chapter](./using_loki.md).
+of `LogQL`? We will look at that in the [next chapter](./using_loki.md).
 
 You can find the full example [here](...).