Merge pull request #103 from adityapatwardhan/PerfTest

Performance Testing

Author: joeyaiello

2-Draft-Accepted/RFCNNN-Performance-Testing.md

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+---
+RFC: 
+Author: Aditya Patwardhan
+Status: Draft
+SupercededBy:
+Version: 0.2
+Area: Testing
+Comments Due: 10/15/2017
+Plan to implement: Yes
+---
+
+# Performance testing for PowerShell
+
+This RFC proposes the plan to add AppInsights instrumentation to collect performance telemetry from daily CI runs.
+This RFC specifies the additional telemetry that will be added.
+
+## Motivation
+
+To validate the performance of PowerShell, we need to gather performance measurements at regular intervals.
+This will enable us in visualizing performance trends and help us identify performance regressions.
+
+## Specification
+
+This RFC proposes to add AppInsights telemetry data points to gather performance metrics.
+These metrics will be collected only during daily CI runs in AppVeyor and Travis CI.
+Typically, we would need large number of iterations to get stable numbers.
+A [metric aggregator](https://docs.microsoft.com/en-us/azure/application-insights/app-insights-api-custom-events-metrics#trackmetric) will be used to compose the data from iterations and then upload the telemetry data points.
+This will avoid throttling and dropping of events.
+
+The metric collection code will be within a `#ifdef` and will only be compiled in when PowerShell is built with `Performance` configuration.
+There will be no performance metric collection code in official builds.
+
+### Proposed performance test scenarios
+
+* PowerShell startup time for cold and warm start.
+
+* `Get-Command` for a particular module.
+
+* `Get-Help` for non-existent command, about topic and cmdlet.
+
+* `Import-Module` for script-based, binary modules.
+
+* `Get-Module -ListAvailable` of a scoped PSModulePath constrained to test modules.
+
+* Parsing of scripts, classes.
+
+Telemetry events will be added to PowerShell code at appropriate locations to collect these metrics.
+Before recording data points, it will be verified that we are running a daily run in AppVeyor or Travis CI.
+PowerBI dashboard will be created to visualize the metrics.
+
+### Environment
+
+* PowerShell assemblies are CrossGen'ed.
+* PSModulePath will be scoped to performance test modules path.
+* Windows, Linux and MacOS have separate AppInsights streams, so they can be tracked separately.
+* All measurements will be for test artifacts to reduce variance due to product module changes.
+
+## Alternate Proposals and Considerations
+
+AppInsights was chosen to achieve cross platform compatibility.
+Another alternative would be to develop a framework to log metric as cross platform module.
+It would be lot of work to create a precise and reliable framework.
+
+Defining goals for these metrics is out of scope for this RFC.
+
+DotNet / CoreFX uses [xUnit performance framework](https://github.com/Microsoft/xunit-performance).
+It requires us the develop the tests in C# and hence we would have to use Powershell APIs to execute tests.
+The lowest granularity for measurement we get would be around `PowerShell.AddScript().Invoke()`.
+This would be too broad of a measurement and might hide the scenario under test.