slabinfo.5: Note constraints for values written to slabinfo

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man5/slabinfo.5

@@ -105,6 +105,17 @@ is the cache name, and
 and
 .IR sharedfactor
 are integers defining new values for the corresponding tunables.
+The
+.I limit
+value should be a positive value,
+.I batchcount
+should be a positive value that is less than or equal to
+.IR limit ,
+and
+.I sharedfactor
+should be nonnegative.
+If any of the specified values is invalid,
+the cache settings are left unchanged.
 
 The
 .I tunables