Ethan,
Some further thought on this:
If a rule is not matching on ‘dp_hash', or is matching on ‘dp_hash’, but not
any L2, L3, or L4 fields, its location has little impact on the generated
datapath masks. Having ‘dp_hash’ at a later stage makes the bond table lookup a
bit less efficient, though, as the lookup typically will need two lookups,
whereas only one would be needed if ‘dp_hash’ was with the 1st stage.
However, if a rule is matching on ‘dp_hash’ and some L2, L3, and/or L4 fields,
it would be better to have it on as early stage as possible to avoid
unwildcarding the bits for the further stages in case of a miss. This is not
the case currently, and as ‘dp_hash’ is not exposed to the controller, this
will likely remain a theoretical consideration.
By this logic it would be better to have ‘dp_hash’ with the ‘L1’ like other
metadata, no?
Jarno
On Apr 3, 2014, at 5:46 PM, Ethan Jackson <et...@nicira.com> wrote:
> Since the dp_hash will often be a hash of the 5 tuple, it makes sense
> to put it with the L4 header so it hits in the last classifier lookup
> stage.
>
> Signed-off-by: Ethan Jackson <et...@nicira.com>
> ---
> lib/flow.h | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/lib/flow.h b/lib/flow.h
> index a6f45c9..7eb79d9 100644
> --- a/lib/flow.h
> +++ b/lib/flow.h
> @@ -97,17 +97,13 @@ union flow_in_port {
> * be looked at. This enables better wildcarding for datapath flows.
> */
> struct flow {
> - /* Recirculation */
> - uint32_t dp_hash; /* Datapath computed hash value. The exact
> - computation is opaque to the user space.*/
> - uint32_t recirc_id; /* Must be exact match. */
> -
> /* L1 */
> struct flow_tnl tunnel; /* Encapsulating tunnel parameters. */
> ovs_be64 metadata; /* OpenFlow Metadata. */
> uint32_t regs[FLOW_N_REGS]; /* Registers. */
> uint32_t skb_priority; /* Packet priority for QoS. */
> uint32_t pkt_mark; /* Packet mark. */
> + uint32_t recirc_id; /* Must be exact match. */
> union flow_in_port in_port; /* Input port.*/
>
> /* L2 */
> @@ -134,6 +130,8 @@ struct flow {
> ovs_be16 pad; /* Padding. */
>
> /* L4 */
> + uint32_t dp_hash; /* Datapath computed hash value. The exact
> + computation is opaque to the user space.*/
> ovs_be16 tp_src; /* TCP/UDP/SCTP source port. */
> ovs_be16 tp_dst; /* TCP/UDP/SCTP destination port.
> * Keep last for the BUILD_ASSERT_DECL below
> */
> --
> 1.8.1.2
>
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