[ovs-dev] [RFC v3 PATCH 3/5] dpif-netdev: Skip encap action during datapath execution

Eli Britstein elibr at mellanox.com
Mon Jun 1 15:48:07 UTC 2020


On 6/1/2020 6:15 PM, Sriharsha Basavapatna wrote:
> On Mon, Jun 1, 2020 at 7:58 PM Eli Britstein <elibr at mellanox.com> wrote:
>>
>> On 5/28/2020 11:19 AM, Sriharsha Basavapatna wrote:
>>> In this patch we check if action processing (apart from OUTPUT action),
>>> should be skipped for a given dp_netdev_flow. Specifically, we check if
>>> the action is TNL_PUSH and if it has been offloaded to HW, then we do not
>>> push the tunnel header in SW. The datapath only executes the OUTPUT action.
>>> The packet will be encapsulated in HW during transmit.
>>>
>>> Signed-off-by: Sriharsha Basavapatna <sriharsha.basavapatna at broadcom.com>
>>> ---
>>>    lib/dpif-netdev.c | 46 ++++++++++++++++++++++++++++++++++++----------
>>>    1 file changed, 36 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
>>> index 781b233f4..3e175c25e 100644
>>> --- a/lib/dpif-netdev.c
>>> +++ b/lib/dpif-netdev.c
>>> @@ -112,6 +112,7 @@ COVERAGE_DEFINE(datapath_drop_recirc_error);
>>>    COVERAGE_DEFINE(datapath_drop_invalid_port);
>>>    COVERAGE_DEFINE(datapath_drop_invalid_tnl_port);
>>>    COVERAGE_DEFINE(datapath_drop_rx_invalid_packet);
>>> +COVERAGE_DEFINE(datapath_skip_tunnel_push);
>>>
>>>    /* Protects against changes to 'dp_netdevs'. */
>>>    static struct ovs_mutex dp_netdev_mutex = OVS_MUTEX_INITIALIZER;
>>> @@ -538,6 +539,16 @@ struct dp_netdev_flow {
>>>        bool dead;
>>>        uint32_t mark;               /* Unique flow mark assigned to a flow */
>>>
>>> +    /* The next two members are used to support partial offloading of
>>> +     * actions. The boolean flag tells if this flow has its actions partially
>>> +     * offloaded. The egress port# tells if the action should be offloaded
>>> +     * on the egress (output) port instead of the in-port for the flow. Note
>>> +     * that we support flows with a single egress port action.
>>> +     * (see MAX_ACTION_ATTRS for related comments).
>>> +     */
>>> +    bool partial_actions_offloaded;
>>> +    odp_port_t  egress_offload_port;
>>> +
>>>        /* Statistics. */
>>>        struct dp_netdev_flow_stats stats;
>>>
>>> @@ -791,7 +802,8 @@ static void dp_netdev_execute_actions(struct dp_netdev_pmd_thread *pmd,
>>>                                          bool should_steal,
>>>                                          const struct flow *flow,
>>>                                          const struct nlattr *actions,
>>> -                                      size_t actions_len);
>>> +                                      size_t actions_len,
>>> +                                      const struct dp_netdev_flow *dp_flow);
>>>    static void dp_netdev_input(struct dp_netdev_pmd_thread *,
>>>                                struct dp_packet_batch *, odp_port_t port_no);
>>>    static void dp_netdev_recirculate(struct dp_netdev_pmd_thread *,
>>> @@ -3828,7 +3840,7 @@ dpif_netdev_execute(struct dpif *dpif, struct dpif_execute *execute)
>>>        dp_packet_batch_init_packet(&pp, execute->packet);
>>>        pp.do_not_steal = true;
>>>        dp_netdev_execute_actions(pmd, &pp, false, execute->flow,
>>> -                              execute->actions, execute->actions_len);
>>> +                              execute->actions, execute->actions_len, NULL);
>>>        dp_netdev_pmd_flush_output_packets(pmd, true);
>>>
>>>        if (pmd->core_id == NON_PMD_CORE_ID) {
>>> @@ -6456,7 +6468,7 @@ packet_batch_per_flow_execute(struct packet_batch_per_flow *batch,
>>>        actions = dp_netdev_flow_get_actions(flow);
>>>
>>>        dp_netdev_execute_actions(pmd, &batch->array, true, &flow->flow,
>>> -                              actions->actions, actions->size);
>>> +                              actions->actions, actions->size, flow);
>>>    }
>>>
>>>    static inline void
>>> @@ -6764,7 +6776,7 @@ handle_packet_upcall(struct dp_netdev_pmd_thread *pmd,
>>>         * we'll send the packet up twice. */
>>>        dp_packet_batch_init_packet(&b, packet);
>>>        dp_netdev_execute_actions(pmd, &b, true, &match.flow,
>>> -                              actions->data, actions->size);
>>> +                              actions->data, actions->size, NULL);
>>>
>>>        add_actions = put_actions->size ? put_actions : actions;
>>>        if (OVS_LIKELY(error != ENOSPC)) {
>>> @@ -6999,6 +7011,7 @@ dp_netdev_recirculate(struct dp_netdev_pmd_thread *pmd,
>>>    struct dp_netdev_execute_aux {
>>>        struct dp_netdev_pmd_thread *pmd;
>>>        const struct flow *flow;
>>> +    const struct dp_netdev_flow *dp_flow;    /* for partial action offload */
>>>    };
>>>
>>>    static void
>>> @@ -7143,7 +7156,7 @@ dp_execute_userspace_action(struct dp_netdev_pmd_thread *pmd,
>>>        if (!error || error == ENOSPC) {
>>>            dp_packet_batch_init_packet(&b, packet);
>>>            dp_netdev_execute_actions(pmd, &b, should_steal, flow,
>>> -                                  actions->data, actions->size);
>>> +                                  actions->data, actions->size, NULL);
>>>        } else if (should_steal) {
>>>            dp_packet_delete(packet);
>>>            COVERAGE_INC(datapath_drop_userspace_action_error);
>>> @@ -7162,6 +7175,7 @@ dp_execute_cb(void *aux_, struct dp_packet_batch *packets_,
>>>        int type = nl_attr_type(a);
>>>        struct tx_port *p;
>>>        uint32_t packet_count, packets_dropped;
>>> +    struct dp_netdev_flow *dp_flow = aux->dp_flow;
>>>
>>>        switch ((enum ovs_action_attr)type) {
>>>        case OVS_ACTION_ATTR_OUTPUT:
>>> @@ -7219,9 +7233,20 @@ dp_execute_cb(void *aux_, struct dp_packet_batch *packets_,
>>>            }
>>>            dp_packet_batch_apply_cutlen(packets_);
>>>            packet_count = dp_packet_batch_size(packets_);
>>> -        if (push_tnl_action(pmd, a, packets_)) {
>>> -            COVERAGE_ADD(datapath_drop_tunnel_push_error,
>>> -                         packet_count);
>>> +        /* Execute tnl_push action in SW, if it is not offloaded as a partial
>>> +         * action in HW. Otherwise, HW pushes the tunnel header during output
>>> +         * processing. There's a small window here in which the offload thread
>>> +         * offloads the flow, but the partial_actions_offloaded flag is still
>>> +         * not set. In this case, as the packet is already encapsulated, it
>>> +         * wouldn't match the offloaded flow and the action won't be executed
>>> +         * in HW.
>> I have created a scenario in which it would hit. Just set the inner
>> properties as the outer. Of course it is not the common case, but it
>> takes only an example.
>>
>> Maybe add a logic not to offload if the matches would apply to the outer.
> The outer properties specifically outer mac addresses are resolved by
> OVS and then added to the header to be pushed. So I'm not sure how you
> created this scenario if I'm correctly understanding your comment. Can
> you please provide some details (example/commands that you used etc)
> to hit the condition ? More clarity on this would help me to add the
> additional logic to decline offload in this case.
I've just manually set the properties of the inner according to my 
setup's outers. Regarding suggestion where to check, please see patch 5/5.
>
> Thanks,
> -Harsha
>>> +         */
>>> +        if (!dp_flow || !dp_flow->partial_actions_offloaded) {
>>> +            if (push_tnl_action(pmd, a, packets_)) {
>>> +                COVERAGE_ADD(datapath_drop_tunnel_push_error, packet_count);
>>> +            }
>>> +        } else {
>>> +            COVERAGE_ADD(datapath_skip_tunnel_push, packet_count);
>>>            }
>>>            return;
>>>
>>> @@ -7509,9 +7534,10 @@ static void
>>>    dp_netdev_execute_actions(struct dp_netdev_pmd_thread *pmd,
>>>                              struct dp_packet_batch *packets,
>>>                              bool should_steal, const struct flow *flow,
>>> -                          const struct nlattr *actions, size_t actions_len)
>>> +                          const struct nlattr *actions, size_t actions_len,
>>> +                          const struct dp_netdev_flow *dp_flow)
>>>    {
>>> -    struct dp_netdev_execute_aux aux = { pmd, flow };
>>> +    struct dp_netdev_execute_aux aux = { pmd, flow, dp_flow };
>>>
>>>        odp_execute_actions(&aux, packets, should_steal, actions,
>>>                            actions_len, dp_execute_cb);


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