[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <76a0c751-c827-4b6e-b27f-ced3ba2834fb@gmx.net>
Date: Mon, 16 Oct 2023 20:25:32 +0200
From: Stefan Wahren <wahrenst@....net>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Neal Cardwell <ncardwell@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Fabio Estevam <festevam@...il.com>, linux-imx@....com,
Stefan Wahren <stefan.wahren@...rgebyte.com>,
Michael Heimpold <mhei@...mpold.de>, netdev@...r.kernel.org,
Yuchung Cheng <ycheng@...gle.com>
Subject: Re: iperf performance regression since Linux 5.18
Hi Eric,
Am 16.10.23 um 12:35 schrieb Eric Dumazet:
> On Mon, Oct 16, 2023 at 11:49 AM Eric Dumazet <edumazet@...gle.com> wrote:
> Speaking of TSQ, it seems an old change (commit 75eefc6c59fd "tcp:
> tsq: add a shortcut in tcp_small_queue_check()")
> has been accidentally removed in 2017 (75c119afe14f "tcp: implement
> rb-tree based retransmit queue")
>
> Could you try this fix:
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 9c8c42c280b7638f0f4d94d68cd2c73e3c6c2bcc..e61a3a381d51b554ec8440928e22a290712f0b6b
> 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2542,6 +2542,18 @@ static bool tcp_pacing_check(struct sock *sk)
> return true;
> }
>
> +static bool tcp_rtx_queue_empty_or_single_skb(const struct sock *sk)
> +{
> + const struct rb_node *node = sk->tcp_rtx_queue.rb_node;
> +
> + /* No skb in the rtx queue. */
> + if (!node)
> + return true;
> +
> + /* Only one skb in rtx queue. */
> + return !node->rb_left && !node->rb_right;
> +}
> +
> /* TCP Small Queues :
> * Control number of packets in qdisc/devices to two packets / or ~1 ms.
> * (These limits are doubled for retransmits)
> @@ -2579,12 +2591,12 @@ static bool tcp_small_queue_check(struct sock
> *sk, const struct sk_buff *skb,
> limit += extra_bytes;
> }
> if (refcount_read(&sk->sk_wmem_alloc) > limit) {
> - /* Always send skb if rtx queue is empty.
> + /* Always send skb if rtx queue is empty or has one skb.
> * No need to wait for TX completion to call us back,
> * after softirq/tasklet schedule.
> * This helps when TX completions are delayed too much.
> */
> - if (tcp_rtx_queue_empty(sk))
> + if (tcp_rtx_queue_empty_or_single_skb(sk))
> return false;
>
> set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
This patch applied on top of Linux 6.1.49, TSO on, gso_max_size 65535,
CONFIG_HZ_100=y
root@...ragon:/boot# iperf -t 10 -i 1 -c 192.168.1.129
------------------------------------------------------------
Client connecting to 192.168.1.129, TCP port 5001
TCP window size: 192 KByte (default)
------------------------------------------------------------
[ 3] local 192.168.1.12 port 59714 connected with 192.168.1.129 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0- 1.0 sec 11.5 MBytes 96.5 Mbits/sec
[ 3] 1.0- 2.0 sec 11.4 MBytes 95.4 Mbits/sec
[ 3] 2.0- 3.0 sec 11.1 MBytes 93.3 Mbits/sec
[ 3] 3.0- 4.0 sec 11.2 MBytes 94.4 Mbits/sec
[ 3] 4.0- 5.0 sec 11.1 MBytes 93.3 Mbits/sec
[ 3] 5.0- 6.0 sec 11.2 MBytes 94.4 Mbits/sec
[ 3] 6.0- 7.0 sec 11.2 MBytes 94.4 Mbits/sec
[ 3] 7.0- 8.0 sec 11.1 MBytes 93.3 Mbits/sec
[ 3] 8.0- 9.0 sec 11.4 MBytes 95.4 Mbits/sec
[ 3] 9.0-10.0 sec 11.2 MBytes 94.4 Mbits/sec
[ 3] 0.0-10.0 sec 113 MBytes 94.4 Mbits/sec
The figures are comparable to disabling TSO -> Good
Thanks
Powered by blists - more mailing lists