netdev - Re: [PATCH net-next v2] net: bcmgenet: collect Rx discarded packet count

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Date:	Tue, 10 Mar 2015 17:08:02 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Petri Gynther <pgynther@...gle.com>
Cc:	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Jaedon Shin <jaedon.shin@...il.com>
Subject: Re: [PATCH net-next v2] net: bcmgenet: collect Rx discarded packet count

2015-03-10 15:55 GMT-07:00 Petri Gynther <pgynther@...gle.com>:
> Bits 31:16 of RDMA_PROD_INDEX contain Rx discarded packet count, which
> are the Rx packets that had to be dropped by MAC hardware since there
> was no room on the Rx queue. Add code to collect this information into
> the netdev stats.
>
> Signed-off-by: Petri Gynther <pgynther@...gle.com>
> ---
>  drivers/net/ethernet/broadcom/genet/bcmgenet.c | 18 ++++++++++++++++++
>  drivers/net/ethernet/broadcom/genet/bcmgenet.h |  1 +
>  2 files changed, 19 insertions(+)
>
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index 275be56..d3be1aeb 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -1384,9 +1384,27 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_priv *priv,
>         int len, err;
>         unsigned int rxpktprocessed = 0, rxpkttoprocess;
>         unsigned int p_index;
> +       unsigned int discards;
>         unsigned int chksum_ok = 0;
>
>         p_index = bcmgenet_rdma_ring_readl(priv, index, RDMA_PROD_INDEX);
> +
> +       discards = (p_index >> DMA_P_INDEX_DISCARD_CNT_SHIFT) &
> +                  DMA_P_INDEX_DISCARD_CNT_MASK;
> +       if (discards > ring->old_discards) {
> +               discards = discards - ring->old_discards;
> +               dev->stats.rx_missed_errors += discards;
> +               dev->stats.rx_errors += discards;
> +               ring->old_discards += discards;
> +
> +               /* Clear HW register when we reach 75% of maximum 0xFFFF */
> +               if (ring->old_discards >= 0xC000) {
> +                       ring->old_discards = 0;
> +                       bcmgenet_rdma_ring_writel(priv, index, 0,
> +                                                 RDMA_PROD_INDEX);
> +               }
> +       }

So this looks better, I am wondering if we should not actually do this
in the case where we run out of memory, because this is pretty much
when the discard counter is likely to be increased?

> +
>         p_index &= DMA_P_INDEX_MASK;
>
>         if (likely(p_index >= ring->c_index))
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.h b/drivers/net/ethernet/broadcom/genet/bcmgenet.h
> index 17443db..2a81138 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.h
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.h
> @@ -548,6 +548,7 @@ struct bcmgenet_rx_ring {
>         unsigned int    read_ptr;       /* Rx ring read pointer */
>         unsigned int    cb_ptr;         /* Rx ring initial CB ptr */
>         unsigned int    end_ptr;        /* Rx ring end CB ptr */
> +       unsigned int    old_discards;
>  };
>
>  /* device context */
> --
> 2.2.0.rc0.207.ga3a616c
>



-- 
Florian
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