[ovs-dev] [PATCH 3/3] dpif-netdev: Calculate rxq cycles prior to rxq_cycle_sort calls.

[Darrell Ball]

Are there any other comments for this patch?


On 8/30/17, 11:01 AM, "Darrell Ball" <dball at vmware.com> wrote:

    Thanks for the patch Kevin
    
    On 8/30/17, 10:45 AM, "Kevin Traynor" <ktraynor at redhat.com> wrote:
    
        rxq_cycle_sort summed the latest cycles from each queue for sorting.
        While each comparison was correct with the latest cycles, the cycles
        could change between calls to rxq_cycle_sort. In order to use
        consistent values through each call to rxq_cycle_sort, sum the cycles
        prior to rxq_cycle_sort being called.
    
    As discussed, these changes are optional and have some tradeoffs, but
    overall, I don’t see any major issue introduced here, since this is understood to be a
    rough comparison anyways.
        
        Also, change return to 0 when values are equal.
    
    As discussed, this means the equal tie-breaker is done by qsort instead of
    the compare function; the net practical effect of this is nil, but this is more
    standard.
    
        Reported-by: Ilya Maximets <i.maximets at samsung.com>
        Signed-off-by: Kevin Traynor <ktraynor at redhat.com>
        ---
         lib/dpif-netdev.c | 22 +++++++++++++---------
         1 file changed, 13 insertions(+), 9 deletions(-)
        
        diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
        index 1db9f10..7c21ee5 100644
        --- a/lib/dpif-netdev.c
        +++ b/lib/dpif-netdev.c
        @@ -3432,18 +3432,14 @@ rxq_cycle_sort(const void *a, const void *b)
             struct dp_netdev_rxq *qb;
             uint64_t total_qa, total_qb;
        -    unsigned i;
         
             qa = *(struct dp_netdev_rxq **) a;
             qb = *(struct dp_netdev_rxq **) b;
         
        -    total_qa = total_qb = 0;
        -    for (i = 0; i < PMD_RXQ_INTERVAL_MAX; i++) {
        -        total_qa += dp_netdev_rxq_get_intrvl_cycles(qa, i);
        -        total_qb += dp_netdev_rxq_get_intrvl_cycles(qb, i);
        -    }
        -    dp_netdev_rxq_set_cycles(qa, RXQ_CYCLES_PROC_HIST, total_qa);
        -    dp_netdev_rxq_set_cycles(qb, RXQ_CYCLES_PROC_HIST, total_qb);
        +    total_qa = dp_netdev_rxq_get_cycles(qa, RXQ_CYCLES_PROC_HIST);
        +    total_qb = dp_netdev_rxq_get_cycles(qb, RXQ_CYCLES_PROC_HIST);
         
        -    if (total_qa >= total_qb) {
        +    if (total_qa == total_qb) {
        +        return 0;
        +    } else if (total_qa > total_qb) {
                 return -1;
             }
        @@ -3493,4 +3489,6 @@ rxq_scheduling(struct dp_netdev *dp, bool pinned) OVS_REQUIRES(dp->port_mutex)
                         }
                     } else if (!pinned && q->core_id == OVS_CORE_UNSPEC) {
        +                uint64_t cycle_hist = 0;
        +
                         if (n_rxqs == 0) {
                             rxqs = xmalloc(sizeof *rxqs);
        @@ -3498,4 +3496,10 @@ rxq_scheduling(struct dp_netdev *dp, bool pinned) OVS_REQUIRES(dp->port_mutex)
                             rxqs = xrealloc(rxqs, sizeof *rxqs * (n_rxqs + 1));
                         }
        +
        +                for (unsigned i = 0; i < PMD_RXQ_INTERVAL_MAX; i++) {
        +                    cycle_hist += dp_netdev_rxq_get_intrvl_cycles(q, i);
        +                }
        +                dp_netdev_rxq_set_cycles(q, RXQ_CYCLES_PROC_HIST, cycle_hist);
        +
                         /* Store the queue. */
                         rxqs[n_rxqs++] = q;
        -- 
        1.8.3.1