I don't really like this. For one thing, Suppose in a particular
stage no changes to the packet are made. There's a good chance you'll
recompute the same hash and still collide.
What if instead, in the emc code if the depth > 0, you folded it into
the hash for the lookup? Very simple change that I think addresses
these issues.
Ethan
On Wed, Apr 15, 2015 at 11:11 AM, Daniele Di Proietto
<diproiet...@vmware.com> wrote:
> Having the same RSS hash after recirculation can cause unnecessary
> collisions in the exact match cache. Setting the RSS hash to 0 forces
> the datapath to compute a new value and account for the changes in the
> packet or in the metadata.
>
> Requested-by: Ethan Jackson <et...@nicira.com>
> Signed-off-by: Daniele Di Proietto <diproiet...@vmware.com>
> ---
> lib/dpif-netdev.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index 20bb498..28262e6 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -3404,6 +3404,10 @@ dp_execute_cb(void *aux_, struct dp_packet **packets,
> int cnt,
>
> err = push_tnl_action(dp, a, packets, cnt);
> if (!err) {
> + for (i = 0; i < cnt; i++) {
> + dp_packet_set_rss_hash(packets[i], 0);
> + }
> +
> (*depth)++;
> dp_netdev_input(pmd, packets, cnt);
> (*depth)--;
> @@ -3433,6 +3437,7 @@ dp_execute_cb(void *aux_, struct dp_packet **packets,
> int cnt,
>
> for (i = 0; i < cnt; i++) {
> packets[i]->md.in_port.odp_port = portno;
> + dp_packet_set_rss_hash(packets[i], 0);
> }
>
> (*depth)++;
> @@ -3491,6 +3496,7 @@ dp_execute_cb(void *aux_, struct dp_packet **packets,
> int cnt,
>
> for (i = 0; i < cnt; i++) {
> packets[i]->md.recirc_id = nl_attr_get_u32(a);
> + dp_packet_set_rss_hash(packets[i], 0);
> }
>
> (*depth)++;
> --
> 2.1.4
>
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