Received-SPF: pass (google.com: domain of linux-kernel+bounces-84675-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Date: Wed, 28 Feb 2024 15:32:41 +0700
From: Bagas Sanjaya <bagasdotme@gmail.com>
To: Abdul Anshad Azeez <abdul-anshad.azeez@broadcom.com>,
	edumazet@google.com, davem@davemloft.net, kuba@kernel.org,
	pabeni@redhat.com, corbet@lwn.net, dsahern@kernel.org,
	Linux Networking <netdev@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Regressions <regressions@lists.linux.dev>
Cc: Boon Ang <boon.ang@broadcom.com>,
	John Savanyo <john.savanyo@broadcom.com>,
	Peter Jonasson <peter.jonasson@broadcom.com>,
	Rajender M <rajender.m@broadcom.com>
Subject: Re: Network performance regression in Linux kernel 6.6 for small
 socket size test cases
Message-ID: <Zd7vqSnT6ocYLuZ4@archie.me>
References: <CALkn8kLOozs5UO52SQa9PR-CiKx_mqW8VF9US94qN+ixyqnkdQ@mail.gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
	protocol="application/pgp-signature"; boundary="aJ0FkAcvBcopWHIX"
Content-Disposition: inline
In-Reply-To: <CALkn8kLOozs5UO52SQa9PR-CiKx_mqW8VF9US94qN+ixyqnkdQ@mail.gmail.com>


--aJ0FkAcvBcopWHIX
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

[also Cc: regressions ML]

On Wed, Feb 28, 2024 at 12:13:27PM +0530, Abdul Anshad Azeez wrote:
> During performance regression workload execution of the Linux
> kernel we observed up to 30% performance decrease in a specific networking
> workload on the 6.6 kernel compared to 6.5 (details below). The regressio=
n is
> reproducible in both Linux VMs running on ESXi and bare metal Linux.
>=20
> Workload details:
>=20
> Benchmark - Netperf TCP_STREAM
> Socket buffer size - 8K
> Message size - 256B
> MTU - 1500B
> Socket option - TCP_NODELAY
> # of STREAMs - 32
> Direction - Uni-Directional Receive
> Duration - 60 Seconds
> NIC - Mellanox Technologies ConnectX-6 Dx EN 100G
> Server Config - Intel(R) Xeon(R) Gold 6348 CPU @ 2.60GHz & 512G Memory
>=20
> Bisect between 6.5 and 6.6 kernel concluded that this regression originat=
ed
> from the below commit:
>=20
> commit - dfa2f0483360d4d6f2324405464c9f281156bd87 (tcp: get rid of
> sysctl_tcp_adv_win_scale)
> Author - Eric Dumazet <edumazet@google.com>
> Link -
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit=
/?id=3D
> dfa2f0483360d4d6f2324405464c9f281156bd87
>=20
> Performance data for (Linux VM on ESXi):
> Test case - TCP_STREAM_RECV Throughput in Gbps
> (for different socket buffer sizes and with constant message size - 256B):
>=20
> Socket buffer size - [LK6.5 vs LK6.6]
> 8K - [8.4 vs 5.9 Gbps]
> 16K - [13.4 vs 10.6 Gbps]
> 32K - [19.1 vs 16.3 Gbps]
> 64K - [19.6 vs 19.7 Gbps]
> Autotune - [19.7 vs 19.6 Gbps]
>=20
> >From the above performance data, we can infer that:
> * Regression is specific to lower fixed socket buffer sizes (8K, 16K & 32=
K).
> * Increasing the socket buffer size gradually decreases the throughput im=
pact.
> * Performance is equal for higher fixed socket size (64K) and Autotune so=
cket
> tests.
>=20
> We would like to know if there are any opportunities for optimization in
> the test cases with small socket sizes.
>=20

Can you verify the regression on current mainline (v6.8-rc6)?

--=20
An old man doll... just what I always wanted! - Clara

--aJ0FkAcvBcopWHIX
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iHUEABYKAB0WIQSSYQ6Cy7oyFNCHrUH2uYlJVVFOowUCZd7vpAAKCRD2uYlJVVFO
o3FWAQDe+PbGL4LW/N1x23XLUSDEsqAGX9WqhwvPNQEir1nE3gEAqt155Cln5op5
oMAlTfo6KFQ5Sl5qdUv70rbcuu4T+gs=
=88Qq
-----END PGP SIGNATURE-----

--aJ0FkAcvBcopWHIX--