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    Subject[PATCH 4.9 011/172] net/mlx5e: Added BW check for DIM decision mechanism
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Tal Gilboa <talgi@mellanox.com>


    [ Upstream commit c3164d2fc48fd4fa0477ab658b644559c3fe9073 ]

    DIM (Dynamically-tuned Interrupt Moderation) is a mechanism designed for
    changing the channel interrupt moderation values in order to reduce CPU
    overhead for all traffic types.
    Until now only interrupt and packet rate were sampled.
    We found a scenario on which we get a false indication since a change in
    DIM caused more aggregation and reduced packet rate while increasing BW.

    We now regard a change as succesfull iff:
    current_BW > (prev_BW + threshold) or
    current_BW ~= prev_BW and current_PR > (prev_PR + threshold) or
    current_BW ~= prev_BW and current_PR ~= prev_PR and
    current_IR < (prev_IR - threshold)
    Where BW = Bandwidth, PR = Packet rate and IR = Interrupt rate

    Improvements (ConnectX-4Lx 25GbE, single RX queue, LRO off)
    --------------------------------------------------
    packet size | before[Mb/s] | after[Mb/s] | gain |
    2B | 343.4 | 359.4 | 4.5% |
    16B | 2739.7 | 2814.8 | 2.7% |
    64B | 9739 | 10185.3 | 4.5% |

    Fixes: cb3c7fd4f839 ("net/mlx5e: Support adaptive RX coalescing")
    Signed-off-by: Tal Gilboa <talgi@mellanox.com>
    Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/ethernet/mellanox/mlx5/core/en.h | 2 +
    drivers/net/ethernet/mellanox/mlx5/core/en_rx_am.c | 41 +++++++++++----------
    2 files changed, 24 insertions(+), 19 deletions(-)

    --- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
    +++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
    @@ -283,12 +283,14 @@ struct mlx5e_dma_info {

    struct mlx5e_rx_am_stats {
    int ppms; /* packets per msec */
    + int bpms; /* bytes per msec */
    int epms; /* events per msec */
    };

    struct mlx5e_rx_am_sample {
    ktime_t time;
    unsigned int pkt_ctr;
    + unsigned int byte_ctr;
    u16 event_ctr;
    };

    --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx_am.c
    +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx_am.c
    @@ -183,28 +183,27 @@ static void mlx5e_am_exit_parking(struct
    mlx5e_am_step(am);
    }

    +#define IS_SIGNIFICANT_DIFF(val, ref) \
    + (((100 * abs((val) - (ref))) / (ref)) > 10) /* more than 10% difference */
    +
    static int mlx5e_am_stats_compare(struct mlx5e_rx_am_stats *curr,
    struct mlx5e_rx_am_stats *prev)
    {
    - int diff;
    -
    - if (!prev->ppms)
    - return curr->ppms ? MLX5E_AM_STATS_BETTER :
    - MLX5E_AM_STATS_SAME;
    -
    - diff = curr->ppms - prev->ppms;
    - if (((100 * abs(diff)) / prev->ppms) > 10) /* more than 10% diff */
    - return (diff > 0) ? MLX5E_AM_STATS_BETTER :
    - MLX5E_AM_STATS_WORSE;
    -
    - if (!prev->epms)
    - return curr->epms ? MLX5E_AM_STATS_WORSE :
    + if (!prev->bpms)
    + return curr->bpms ? MLX5E_AM_STATS_BETTER :
    MLX5E_AM_STATS_SAME;

    - diff = curr->epms - prev->epms;
    - if (((100 * abs(diff)) / prev->epms) > 10) /* more than 10% diff */
    - return (diff < 0) ? MLX5E_AM_STATS_BETTER :
    - MLX5E_AM_STATS_WORSE;
    + if (IS_SIGNIFICANT_DIFF(curr->bpms, prev->bpms))
    + return (curr->bpms > prev->bpms) ? MLX5E_AM_STATS_BETTER :
    + MLX5E_AM_STATS_WORSE;
    +
    + if (IS_SIGNIFICANT_DIFF(curr->ppms, prev->ppms))
    + return (curr->ppms > prev->ppms) ? MLX5E_AM_STATS_BETTER :
    + MLX5E_AM_STATS_WORSE;
    +
    + if (IS_SIGNIFICANT_DIFF(curr->epms, prev->epms))
    + return (curr->epms < prev->epms) ? MLX5E_AM_STATS_BETTER :
    + MLX5E_AM_STATS_WORSE;

    return MLX5E_AM_STATS_SAME;
    }
    @@ -266,6 +265,7 @@ static void mlx5e_am_sample(struct mlx5e
    {
    s->time = ktime_get();
    s->pkt_ctr = rq->stats.packets;
    + s->byte_ctr = rq->stats.bytes;
    s->event_ctr = rq->cq.event_ctr;
    }

    @@ -278,12 +278,15 @@ static void mlx5e_am_calc_stats(struct m
    /* u32 holds up to 71 minutes, should be enough */
    u32 delta_us = ktime_us_delta(end->time, start->time);
    unsigned int npkts = end->pkt_ctr - start->pkt_ctr;
    + unsigned int nbytes = end->byte_ctr - start->byte_ctr;

    if (!delta_us)
    return;

    - curr_stats->ppms = (npkts * USEC_PER_MSEC) / delta_us;
    - curr_stats->epms = (MLX5E_AM_NEVENTS * USEC_PER_MSEC) / delta_us;
    + curr_stats->ppms = DIV_ROUND_UP(npkts * USEC_PER_MSEC, delta_us);
    + curr_stats->bpms = DIV_ROUND_UP(nbytes * USEC_PER_MSEC, delta_us);
    + curr_stats->epms = DIV_ROUND_UP(MLX5E_AM_NEVENTS * USEC_PER_MSEC,
    + delta_us);
    }

    void mlx5e_rx_am_work(struct work_struct *work)

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