docs: Start section on performance impact

README.md

@@ -11,3 +11,20 @@ No further configuration is needed.
 
 ### Pack authors
 Please head to the [wiki](https://pages.frohnmeyer-wds.de/JfMods/Respackopts/) for details on how to use respackopts in a pack.
+
+# Performance Impact
+Performance always depends on factors other than the game itself like disk speed, resource usage by other programs, the OS you are using, etc.
+These measurements were taken with Minecraft 1.20.1, Fabric Loader 0.14.21, Fabric API 0.84.0, LibJF 3.8.0 and 
+Therefore, please do not assume these measurements to be accurate for all use cases.
+
+LibJF injects hooks into the resource loader, meaning there is additional overhead for every resource access.
+In practice, this results in a five percent increase in resource reloading time over vanilla and an eight percent increase in game load times over vanilla (.2 seconds).
+
+Respackopts uses those hooks and additional mixins to work, adding additional overhead.
+In practice, this results in a six percent increase in resource reloading time over vanilla and an eighteen percent increase in game load times over vanilla (.43 seconds).
+
+The most significant increase is measurable during pack scanning, which takes nearly 100 times longer when comparing Minecraft with Respackopts to vanilla.
+This is because Respackopts performs and caches most parsing and computation during this stage.
+As the statistic for game loading shows, this is not necessarily noticeable during startup, because the total is still comparably small.
+It is only noticeable in the resource pack screen, where scanning is performed every 20 ticks and whenever the screen is resized and the impact is much larger.
+For this reason, I have created [a separate mod](https://modrinth.com/mod/async-pack-scan) that tweaks that screen for increased performance.