A really useful feature of the CLR is that it allows a user to request a new JIT (aka 'reJIT'). This is really important for vendors who want to manipulate the IL, one reason may be that the end users would like to increase the instrumentation level, after completing the rewrite you would request a reJIT to apply the changes to the app without restarting.One glaring limitation of this feature was that In order to enable ReJIT, your profiler would need to be loaded at startup, and set an immutable flag in the Initialize method to enable the ReJIT. In very practical terms this means that if you walked up to a running application and decided you wanted to start ad hoc profiling you would need to restart the application which is not always practical.As of .Net Core 3 preview5 any profiler ...