From: Brett A C Sheffield <bacs@librecast.net>
To: Simon Schippers <simon.schippers@tu-dortmund.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
Jason Wang <jasowangio@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, Simon Horman <horms@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Shuah Khan <skhan@linuxfoundation.org>,
Andrew Lunn <andrew+netdev@lunn.ch>,
Tim Gebauer <tim.gebauer@tu-dortmund.de>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net v2] tun/tap & vhost-net: make qdisc backpressure opt-in via IFF_BACKPRESSURE
Date: Tue, 7 Jul 2026 22:05:52 +0200 [thread overview]
Message-ID: <ak1cIAwQzKS35x0m@karahi.librecast.net> (raw)
In-Reply-To: <0d28fdc4-3c03-48d6-bd59-e59f7a01f4b6@tu-dortmund.de>
On 2026-07-07 08:52, Simon Schippers wrote:
> Brett, can you try the two attached patches here with iperf3?
> I think testing with 8 and 16 threads is enough, so where there is a
> regression.
>
> The two patches are about time when to wake:
> Currently we wake after consuming half the internal ring buffer.
> One of the attached patches wakes after 2 cachelines (128 of 1000
> packets) and the other one just wakes once the ring buffer is empty.
>
> This would really help :)
Sure...
7.2.0-rc2 (unpatched)
threads 1
[ 5] 0.00-10.00 sec 20.4 GBytes 17.5 Gbits/sec 0 sender
[ 5] 0.00-10.00 sec 2.00 GBytes 1.72 Gbits/sec receiver
threads 2
[SUM] 0.00-10.00 sec 12.7 GBytes 10.9 Gbits/sec 0 sender
[SUM] 0.00-10.00 sec 4.00 GBytes 3.43 Gbits/sec receiver
threads 8
[SUM] 0.00-10.00 sec 11.5 GBytes 9.85 Gbits/sec 0 sender
[SUM] 0.00-10.01 sec 11.4 GBytes 9.83 Gbits/sec receiver
threads 16
[SUM] 0.00-10.00 sec 11.6 GBytes 9.95 Gbits/sec 0 sender
[SUM] 0.00-10.01 sec 11.5 GBytes 9.91 Gbits/sec receiver
7.2.0-rc2 with 0001-tun-set-waking-threshold-to-ptr_ring_empty.patch
threads 1
[ 5] 0.00-10.00 sec 19.6 GBytes 16.8 Gbits/sec 0 sender
[ 5] 0.00-10.00 sec 2.00 GBytes 1.72 Gbits/sec receiver
threads 2
[SUM] 0.00-10.00 sec 11.1 GBytes 9.50 Gbits/sec 0 sender
[SUM] 0.00-10.00 sec 4.00 GBytes 3.43 Gbits/sec receiver
threads 8
[SUM] 0.00-10.00 sec 10.8 GBytes 9.25 Gbits/sec 0 sender
[SUM] 0.00-10.01 sec 10.7 GBytes 9.23 Gbits/sec receiver
threads 16
[SUM] 0.00-10.00 sec 10.9 GBytes 9.34 Gbits/sec 0 sender
[SUM] 0.00-10.01 sec 10.8 GBytes 9.30 Gbits/sec receiver
7.2.0-rc2 with 0001-tun-set-waking-threshold-to-tx_ring.batch.patch
threads 1
[ 5] 0.00-10.00 sec 19.6 GBytes 16.9 Gbits/sec 2 sender
[ 5] 0.00-10.00 sec 2.00 GBytes 1.72 Gbits/sec receiver
threads 2
[SUM] 0.00-10.00 sec 13.9 GBytes 11.9 Gbits/sec 0 sender
[SUM] 0.00-10.00 sec 4.00 GBytes 3.43 Gbits/sec receiver
threads 8
[SUM] 0.00-10.00 sec 12.7 GBytes 10.9 Gbits/sec 0 sender
[SUM] 0.00-10.01 sec 12.3 GBytes 10.6 Gbits/sec receiver
threads 16
[SUM] 0.00-10.00 sec 12.5 GBytes 10.7 Gbits/sec 0 sender
[SUM] 0.00-10.00 sec 12.4 GBytes 10.7 Gbits/sec receiver
HTH,
Brett
--
Brett Sheffield (he/him)
Librecast - Decentralising the Internet with Multicast
https://librecast.net/
https://blog.brettsheffield.com/
prev parent reply other threads:[~2026-07-07 20:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-06 9:42 [PATCH net v2] tun/tap & vhost-net: make qdisc backpressure opt-in via IFF_BACKPRESSURE Simon Schippers
2026-07-06 10:11 ` Brett A C Sheffield
2026-07-06 13:23 ` Michael S. Tsirkin
2026-07-06 15:33 ` Simon Schippers
2026-07-06 17:10 ` Brett A C Sheffield
2026-07-07 6:52 ` Simon Schippers
2026-07-07 6:56 ` Simon Schippers
2026-07-07 20:05 ` Brett A C Sheffield [this message]
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