update readme

README.md

@@ -1,7 +1,20 @@
 
 # memavaild
 
-A new way to improve responsiveness during intense swapping.
+[![Total alerts](https://img.shields.io/lgtm/alerts/g/hakavlad/memavaild.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/hakavlad/memavaild/alerts/)
+[![Language grade: Python](https://img.shields.io/lgtm/grade/python/g/hakavlad/memavaild.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/hakavlad/memavaild/context:python)
+
+Improve responsiveness during intense swapping: keep amount of available memory.
+
+## Requirements
+
+- Python 3.3+
+- systemd with unified cgroup hierarchy
+
+## Known problems
+
+- Awful documentation.
+- The ZFS ARC cache is memory-reclaimable, like the Linux buffer cache. However, in contrast to the buffer cache, it currently does not count to MemAvailable (see openzfs/zfs#10255).
 
 ## Install
 ```