From: Matthieu Baerts <matttbe@kernel.org>
To: Alice Mikityanska <alice.kernel@fastmail.im>,
Paolo Abeni <pabeni@redhat.com>, Jakub Kicinski <kuba@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>,
"David S. Miller" <davem@davemloft.net>,
Simon Horman <horms@kernel.org>, Shuah Khan <shuah@kernel.org>,
netdev@vger.kernel.org, linux-kselftest@vger.kernel.org,
Alice Mikityanska <alice@isovalent.com>
Subject: Re: [PATCH net-next 4/4] selftests: net: Fix slow configurations in big_tcp_tunnels.sh
Date: Wed, 19 Aug 2026 11:25:19 +0200 [thread overview]
Message-ID: <4a8f39cb-655d-42dd-b776-a272e5d34466@kernel.org> (raw)
In-Reply-To: <20260814194124.3102581-5-alice.kernel@fastmail.im>
Hi Alice,
On 14/08/2026 21:41, Alice Mikityanska wrote:
> From: Alice Mikityanska <alice@isovalent.com>
>
> The combination of checksum offload disabled (that causes software GSO)
> and CONFIG_DEBUG_NET=y is inherently slow. Depending on the CPU power
> and load, RTT may increase, limiting sk_pacing_rate, so tcp_tso_autosize
> caps SKBs at around 40 segments, and zero BIG TCP packets are produced.
>
> Increase sysctl net.ipv4.tcp_min_tso_segs and set a bigger initial value
> of CWND in these configurations to force BIG TCP.
Just an innocent question: would it affect the test somehow if the
sysctl and initial cwnd is always modified, not just for a specific config?
(Note that apart from looking at ${KSFT_MACHINE_SLOW} in patch 2, I
think the series looks good to me, and can probably be sent to net after
the merge with net-next.)
Cheers,
Matt
prev parent reply other threads:[~2026-08-19 9:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-14 19:41 [PATCH net-next 0/4] Improve stability of big_tcp_tunnels.sh selftest Alice Mikityanska
2026-08-14 19:41 ` [PATCH net-next 1/4] selftests: net: Wait for netserver to launch Alice Mikityanska
2026-08-14 19:41 ` [PATCH net-next 2/4] selftests: net: Lower threshold on debug kernels for big_tcp_tunnels.sh Alice Mikityanska
2026-08-14 23:07 ` Matthieu Baerts
2026-08-14 19:41 ` [PATCH net-next 3/4] selftests: net: Lower threshold with csum offload off in big_tcp_tunnels.sh Alice Mikityanska
2026-08-14 19:41 ` [PATCH net-next 4/4] selftests: net: Fix slow configurations " Alice Mikityanska
2026-08-19 9:25 ` Matthieu Baerts [this message]
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