netdev - Re: [PATCH net-next] virtio-net: Reduce debug name field size to 16 bytes

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Date:   Mon, 23 Jan 2023 19:42:35 +0530
From:   Pavan Chebbi <pavan.chebbi@...adcom.com>
To:     Parav Pandit <parav@...dia.com>
Cc:     mst@...hat.com, jasowang@...hat.com, netdev@...r.kernel.org,
        davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
        pabeni@...hat.com, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next] virtio-net: Reduce debug name field size to 16 bytes

On Mon, Jan 23, 2023 at 9:25 AM Parav Pandit <parav@...dia.com> wrote:
>
> virtio queue index can be maximum of 65535. 16 bytes are enough to store
> the vq name with the existing string prefix.
>
> With this change, send queue struct saves 24 bytes and receive
> queue saves whole cache line worth 64 bytes per structure
> due to saving in alignment bytes.
>
> Pahole results before:
>
> pahole -s drivers/net/virtio_net.o | \
>     grep -e "send_queue" -e "receive_queue"
> send_queue      1112    0
> receive_queue   1280    1
>
> Pahole results after:
> pahole -s drivers/net/virtio_net.o | \
>     grep -e "send_queue" -e "receive_queue"
> send_queue      1088    0
> receive_queue   1216    1
>
> Signed-off-by: Parav Pandit <parav@...dia.com>
> ---
>  drivers/net/virtio_net.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index a170b0075dcf..3855b8524300 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -134,7 +134,7 @@ struct send_queue {
>         struct scatterlist sg[MAX_SKB_FRAGS + 2];
>
>         /* Name of the send queue: output.$index */
> -       char name[40];
> +       char name[16];
>
>         struct virtnet_sq_stats stats;
>
> @@ -171,7 +171,7 @@ struct receive_queue {
>         unsigned int min_buf_len;
>
>         /* Name of this receive queue: input.$index */
> -       char name[40];
> +       char name[16];
>
>         struct xdp_rxq_info xdp_rxq;
>  };
> --
> 2.26.2
>

Looks good to me.
Reviewed-by: Pavan Chebbi <pavan.chebbi@...adcom.com>

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