Updated COMMAND System (markdown)

COMMAND-System.md

@@ -1,12 +1,35 @@
-# The `system.*` Command Group
+The `system.*` Command Group
+============================
 
 WIP: see list here [
 Comprehensive list of rTorrent 0.9 commands](https://github.com/rakshasa/rtorrent/wiki/rTorrent-0.9-Comprehensive-Command-list-(WIP)#system)
 
-## system.env=NAME (since 0.9.7)
+
+system.env=NAME (since 0.9.7)
+-----------------------------
 
 Query the value of an environment variable, returns an empty string if `NAME` is not defined. Example:
 
 ```ini
 session.path.set=(cat,(system.env,RTORRENT_HOME),"/.session")
-```
+```
+
+
+system.files.advise_random.set=FALSE|true
+-----------------------------------------
+
+When false (default), do not advise files and memory mapped chunks. The kernel uses the default which is most likely some form of sequential read-ahead.
+
+When true, advice file and memory mapped chunks to use POSIX_FADV_RANDOM and MADV_RANDOM. This optimizes for random access reads.
+
+Advise during full torrent hashing is controlled by `system.files.advise_random.hashing.set`.
+
+
+system.files.advise_random.hashing.set=FALSE|true
+-------------------------------------------------
+
+When false (default), do not advise files and memory mapped chunks during full torrent hash checking. The kernel uses the default which is most likely some form of sequential read-ahead.
+
+When true, advise file and memory mapped chunks to use POSIX_FADV_RANDOM and MADV_RANDOM during full torrent hash checking.
+
+This does not affect files or chunks hashed during download.