Add comments on CUDA usage in suricata.yaml.

suricata.yaml

@@ -4,6 +4,10 @@
 # Number of packets allowed to be processed simultaneously.  Default is a
 # conservative 50. a higher number will make sure CPU's/CPU cores will be
 # more easily kept busy, but will negatively impact caching.
+#
+# If you are using the CUDA pattern matcher (b2g_cuda below), different rules
+# apply. In that case try something like 4000 or more. This is because the CUDA
+# pattern matcher scans many packets in parallel.
 #max-pending-packets: 50
 
 # Set the order of alerts bassed on actions
@@ -118,6 +122,10 @@ threading:
 
 # Select the multi pattern algorithm you want to run for scan/search the
 # in the engine. The supported algorithms are b2g, b3g and wumanber.
+#
+# There is also a CUDA pattern matcher (only available if Suricata was
+# compiled with --enable-cuda: b2g_cuda. Make sure to update your
+# max-pending-packets setting above as well if you use b2g_cuda.
 
 mpm-algo: b2g