netdev - Re: [PATCH] sis900: re-enable high throughput

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Date:   Fri, 7 Jun 2019 19:31:40 +0200
From:   Sergej Benilov <sergej.benilov@...glemail.com>
To:     venza@...wnhat.org, netdev@...r.kernel.org
Subject: Re: [PATCH] sis900: re-enable high throughput

On Fri, 7 Jun 2019 at 19:26, Sergej Benilov
<sergej.benilov@...glemail.com> wrote:
>
> Since commit 605ad7f184b60cfaacbc038aa6c55ee68dee3c89 "tcp: refine TSO autosizing",
> the TSQ limit is computed as the smaller of
> sysctl_tcp_limit_output_bytes and max(2 * skb->truesize, sk->sk_pacing_rate >> 10).
> For some connections this approach sets a low limit, reducing throughput dramatically.
>
> Add a call to skb_orphan() to sis900_start_xmit()
> to speed up packets delivery from the kernel to the driver.
>
> Test:
> netperf -H remote -l -2000000 -- -s 1000000
>
> before patch:
>
> MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to remote () port 0 AF_INET : demo
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
>
>  87380 327680 327680    341.79      0.05
>
> after patch:
>
> MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to remote () port 0 AF_INET : demo
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
>
>  87380 327680 327680    1.29       12.54
>
> Signed-off-by: Sergej Benilov <sergej.benilov@...glemail.com>
> ---
>  drivers/net/ethernet/sis/sis900.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/ethernet/sis/sis900.c b/drivers/net/ethernet/sis/sis900.c
> index fd812d2e..ca17b50c 100644
> --- a/drivers/net/ethernet/sis/sis900.c
> +++ b/drivers/net/ethernet/sis/sis900.c
> @@ -1604,6 +1604,7 @@ sis900_start_xmit(struct sk_buff *skb, struct net_device *net_dev)
>         unsigned int  index_cur_tx, index_dirty_tx;
>         unsigned int  count_dirty_tx;
>
> +       skb_orphan(skb);
>         spin_lock_irqsave(&sis_priv->lock, flags);
>
>         /* Calculate the next Tx descriptor entry. */
> --
> 2.17.1
>

Thanks to Eric Dumazet for suggesting this patch