ofproto-dpif: Increase dp_hash default max buckets.

Currently when a user creates an openflow group with with multiple
buckets without specifying a selection type, the efficient dp_hash is
only selected if the user is creating fewer than 64 buckets. But when
dp_hash is explicitly selected, up to 256 buckets are supported.

While up to 64 buckets seems like a lot, certain OVN/Open Stack
workloads could result in the user creating more than 64 buckets. For
example, when using OVN to load balance. This patch increases the
default maximum from 64 to 256.

This change to the default limit doesn't affect how many buckets are
actually created, that is specified by the user when the group is
created, just how traffic is distributed across buckets.

Signed-off-by: Mike Pattrick <mkp@redhat.com>
Acked-by: Gaetan Rivet <grive@u256.net>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/utilities/ovs-ofctl.8.in b/utilities/ovs-ofctl.8.in
index 2017c6eba..e903ca12b 100644
--- a/utilities/ovs-ofctl.8.in
+++ b/utilities/ovs-ofctl.8.in
@@ -1083,8 +1083,9 @@ This field is optional for \fBadd\-group\fR, \fBadd\-groups\fR and
 otherwise.  If no selection method is specified, Open vSwitch up to
 release 2.9 applies the \fBhash\fR method with default fields. From
 2.10 onwards Open vSwitch defaults to the \fBdp_hash\fR method with symmetric
-L3/L4 hash algorithm, unless the weighted group buckets cannot be mapped to
-a maximum of 64 dp_hash values with sufficient accuracy.
+L3/L4 hash algorithm, as long as the weighted group buckets can be mapped to
+dp_hash values with sufficient accuracy.  In 2.10 this was restricted to a
+maximum of 64 buckets, and in 2.17 the limit was raised to 256 buckets.
 In those rare cases Open vSwitch 2.10 and later fall back to the \fBhash\fR
 method with the default set of hash fields.
 .RS