netdev - Re: [net-next PATCH 0/3] Symmetric queue selection using XPS for Rx queues

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Message-ID: <CANn89iJU9Hes3cOEjA1K+g0=yKLyRgZ2YcLqeZ4m+kd=+oqQWA@mail.gmail.com>
Date:   Fri, 20 Apr 2018 02:41:54 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     amritha.nambiar@...el.com
Cc:     netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Tom Herbert <tom@...bertland.com>
Subject: Re: [net-next PATCH 0/3] Symmetric queue selection using XPS for Rx queues

On Thu, Apr 19, 2018 at 6:07 PM Amritha Nambiar <amritha.nambiar@...el.com>
wrote:

> This patch series implements support for Tx queue selection based on
> Rx queue map. This is done by configuring Rx queue map per Tx-queue
> using sysfs attribute. If the user configuration for Rx queues does
> not apply, then the Tx queue selection falls back to XPS using CPUs and
> finally to hashing.

> XPS is refactored to support Tx queue selection based on either the
> CPU map or the Rx-queue map. The config option CONFIG_XPS needs to be
> enabled. By default no receive queues are configured for the Tx queue.

> - /sys/class/net/eth0/queues/tx-*/xps_rxqs

> This is to enable sending packets on the same Tx-Rx queue pair as this
> is useful for busy polling multi-threaded workloads where it is not
> possible to pin the threads to a CPU. This is a rework of Sridhar's
> patch for symmetric queueing via socket option:
> https://www.spinics.net/lists/netdev/msg453106.html

> ---

> Amritha Nambiar (3):
>        net: Refactor XPS for CPUs and Rx queues
>        net: Enable Tx queue selection based on Rx queues
>        net-sysfs: Add interface for Rx queue map per Tx queue


>   include/linux/netdevice.h |   82 +++++++++++++++
>   include/net/sock.h        |   18 +++
>   net/core/dev.c            |  240
+++++++++++++++++++++++++++++++--------------
>   net/core/net-sysfs.c      |   85 ++++++++++++++++
>   net/core/sock.c           |    5 +
>   net/ipv4/tcp_input.c      |    7 +
>   net/ipv4/tcp_ipv4.c       |    1
>   net/ipv4/tcp_minisocks.c  |    1
>   8 files changed, 357 insertions(+), 82 deletions(-)


Without a clear documentation (for example in
Documentation/networking/scaling.txt)
, I really do not understand what problem you want to solve, and why we
need ~300 additional LOC in kernel.

Referring to an old thread (
https://www.spinics.net/lists/netdev/msg453106.html ) is not the way to go.

Sorry :/