doc: Add a performance note for log filtering

Add a not under the log-filter command to indicate
that, while filtering reduces load on the system by
large margins, there may still be a small performance
hit from filtering those.

Signed-off-by: Stephen Worley <sworley@cumulusnetworks.com>

diff --git a/doc/user/basic.rst b/doc/user/basic.rst
index 8395087e8d7b39edcbcb8a0eda5ded51e46afe4b..5509fd5f0d448a323645b113841e5ec78f7a9efd 100644 (file)
--- a/doc/user/basic.rst
+++ b/doc/user/basic.rst
@@ -199,6 +199,13 @@ Basic Config Commands
    will only be printed if it matches on one of the filters in the log-filter
    table. Can be daemon independent.
 
+   .. note::
+
+      Log filters help when you need to turn on debugs that cause significant
+      load on the system (enabling certain debugs can bring FRR to a halt).
+      Log filters prevent this but you should still expect a small performance
+      hit due to filtering each of all those logs.
+
 .. index:: log-filter clear [DAEMON]
 .. clicmd:: log-filter clear [DAEMON]