[ovs-dev] [PATCH v3 2/4] dpif-netdev: Avoid reading RSS hash when EMC is disabled

[Darrell Ball]

Hi Antonio

Can the dependency of this Patch 2 on Patch 1 be removed, while Patch 1 is being discussed ?

Thanks Darrell 

On 8/13/17, 11:32 PM, "ovs-dev-bounces at openvswitch.org on behalf of Darrell Ball" <ovs-dev-bounces at openvswitch.org on behalf of dball at vmware.com> wrote:

    I did not try it yet, but seems reasonable
    If the hash is needed for something else, it will be read at that point. 
    
    -----Original Message-----
    From: <ovs-dev-bounces at openvswitch.org> on behalf of "antonio.fischetti at intel.com" <antonio.fischetti at intel.com>
    Date: Friday, August 11, 2017 at 8:52 AM
    To: "dev at openvswitch.org" <dev at openvswitch.org>
    Subject: [ovs-dev] [PATCH v3 2/4] dpif-netdev: Avoid reading RSS hash when	EMC is disabled
    
        When EMC is disabled the reading of RSS hash is skipped.
        Also, for packets that are not recirculated it retrieves the hash
        value without considering the recirc id.
        
        Signed-off-by: Antonio Fischetti <antonio.fischetti at intel.com>
        ---
        This patch depends on previous patch in this series.
        
        Port-to-Port Test
        =================
        Software built with "-O2 -march=native -g".
        
        I measured the Rx rate regardless of pkt loss by sending 1 UDP flow,
        64B packets, at the line-rate.
        
        2 PMDs with 3 Tx queues.
        
        Flows setup:
          in_port=dpdk0 actions=output:dpdk1
          in_port=dpdk1 actions=output:dpdk0
        
        Results
        -------
        Values are for the Rx rate in Mpps, regardless of packet loss.
        
        RSS column:
           Yes: RSS hash is provided by the NIC
           No: RSS is disabled and the 5-tuple hash must be
               computed in software.
        
        EMC column:
           Yes: default probability insertion,
           No: EMC disabled.
        
        Orig OvS-DPDK means Commit ID:
          6b1babacc3ca0488e07596bf822fe356c9bab646
        
                    +--------------+----------------+----------------+
        +-----+-----+    Orig      | Orig + patch 1 | Orig + patch 1 |
        | RSS | EMC |              |                |  this patch    |
        +-----+-----+--------------+----------------+----------------+
        | Yes | Yes | 11.99, 11.41 | 12.20, 11.31   | 12.20, 11.31   |
        | Yes |  No |  8.32,  8.42 |  8.35,  8.39   |  8.62, 8.62    |
        +-----+-----+--------------+----------------+----------------+
        |  No | Yes |  9.87, 11.15 |  9.79, 11.20   |  9.85, 11.09   |
        |  No |  No |  7.82,  7.84 |  7.84,  7.93   |  8.40,  8.38   |
        +-----+-----+--------------+----------------+----------------+
        ---
         lib/dpif-netdev.c | 20 +++++++++++++++++++-
         1 file changed, 19 insertions(+), 1 deletion(-)
        
        diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
        index 8f6b96b..0db6f83 100644
        --- a/lib/dpif-netdev.c
        +++ b/lib/dpif-netdev.c
        @@ -4578,6 +4578,22 @@ dp_netdev_upcall(struct dp_netdev_pmd_thread *pmd, struct dp_packet *packet_,
         }
         
         static inline uint32_t
        +dpif_netdev_packet_get_rss_hash_orig_pkt(struct dp_packet *packet,
        +                                const struct miniflow *mf)
        +{
        +    uint32_t hash;
        +
        +    if (OVS_LIKELY(dp_packet_rss_valid(packet))) {
        +        hash = dp_packet_get_rss_hash(packet);
        +    } else {
        +        hash = miniflow_hash_5tuple(mf, 0);
        +        dp_packet_set_rss_hash(packet, hash);
        +    }
        +
        +    return hash;
        +}
        +
        +static inline uint32_t
         dpif_netdev_packet_get_rss_hash(struct dp_packet *packet,
                                         const struct miniflow *mf)
         {
        @@ -4715,7 +4731,6 @@ emc_processing(struct dp_netdev_pmd_thread *pmd,
                 }
                 miniflow_extract(packet, &key->mf);
                 key->len = 0; /* Not computed yet. */
        -        key->hash = dpif_netdev_packet_get_rss_hash(packet, &key->mf);
         
                 /*
                  * EMC lookup is skipped when one or both of the following
        @@ -4732,9 +4747,12 @@ emc_processing(struct dp_netdev_pmd_thread *pmd,
                  */
                 if (OVS_LIKELY(cur_min)) {
                     if (!md_is_valid) {
        +                key->hash = dpif_netdev_packet_get_rss_hash_orig_pkt(packet,
        +                        &key->mf);
                         flow = emc_lookup(flow_cache, key);
                     } else {
                         /* Recirculated packet. */
        +                key->hash = dpif_netdev_packet_get_rss_hash(packet, &key->mf);
                         if (flow_cache->n_entries & EMC_RECIRCT_NO_INSERT_THRESHOLD) {
                             /* EMC occupancy is over the threshold.  We skip EMC
                              * lookup for recirculated packets. */
        -- 
        2.4.11
        
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