acl-plugin: tm: add tuplemerge algorithm for relaxing the hashtable masks

Slightly refactored from the initial implementation of the TupleMerge [1]
algorithm by Valerio Bruschi (valerio.bruschi@telecom-paristech.fr)

[1] James Daly, Eric Torng "TupleMerge: Building Online Packet Classifiers
by Omitting Bits", In Proc. IEEE ICCCN 2017, pp. 1-10

Also add startup parameters to turn on/off the algorithm ("use tuple merge 1/0"),
and a startup parameter to be able to tweak the split threshold
("tuple merge split threshold N"), the default value of the split threshold
is 39 as per paper, but some more tuning might be necessary to find the best
value.

This change, alongside with the optimizations which avoid extra lookups,
significantly reduces the slowdown on the ClassBench generated ACLs, which
are supposed to resemble realistic ACLs seen in use in the field.

Change-Id: I9713e4673970e9a62d4d9e9718365293375fab7b
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/plugins/acl/acl.h b/src/plugins/acl/acl.h
index 733d785d886..b994b8506b7 100644
--- a/src/plugins/acl/acl.h
+++ b/src/plugins/acl/acl.h
@@ -194,6 +194,13 @@ typedef struct {
   /* Do we use hash-based ACL matching or linear */
   int use_hash_acl_matching;
 
+  /* Do we use the TupleMerge for hash ACLs or not */
+  int use_tuple_merge;
+
+  /* Max collision vector length before splitting the tuple */
+#define TM_SPLIT_THRESHOLD 39
+  int tuple_merge_split_threshold;
+
   /* a pool of all mask types present in all ACEs */
   ace_mask_type_entry_t *ace_mask_type_pool;