linux-kernel - Re: [Question] ixgbe：Mechanism of RSS

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Message-ID: <CANn89iKVVS=ODm9jKnwG0d_FNUJ7zdYxeDYDyyOb74y3ELJLdA@mail.gmail.com>
Date: Thu, 2 Jan 2025 09:13:55 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Haifeng Xu <haifeng.xu@...pee.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>, 
	", Przemek Kitszel" <przemyslaw.kitszel@...el.com>, ", David S. Miller" <davem@...emloft.net>, 
	", Jakub Kicinski" <kuba@...nel.org>, ", Paolo Abeni" <pabeni@...hat.com>, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org
Subject: Re: [Question] ixgbe：Mechanism of RSS

On Thu, Jan 2, 2025 at 4:53 AM Haifeng Xu <haifeng.xu@...pee.com> wrote:
>
> Hi masters,
>
>         We use the Intel Corporation 82599ES NIC in our production environment. And it has 63 rx queues, every rx queue interrupt is processed by a single cpu.
>         The RSS configuration can be seen as follow:
>
>         RX flow hash indirection table for eno5 with 63 RX ring(s):
>         0:      0     1     2     3     4     5     6     7
>         8:      8     9    10    11    12    13    14    15
>         16:      0     1     2     3     4     5     6     7
>         24:      8     9    10    11    12    13    14    15
>         32:      0     1     2     3     4     5     6     7
>         40:      8     9    10    11    12    13    14    15
>         48:      0     1     2     3     4     5     6     7
>         56:      8     9    10    11    12    13    14    15
>         64:      0     1     2     3     4     5     6     7
>         72:      8     9    10    11    12    13    14    15
>         80:      0     1     2     3     4     5     6     7
>         88:      8     9    10    11    12    13    14    15
>         96:      0     1     2     3     4     5     6     7
>         104:      8     9    10    11    12    13    14    15
>         112:      0     1     2     3     4     5     6     7
>         120:      8     9    10    11    12    13    14    15
>
>         The maximum number of RSS queues is 16. So I have some questions about this. Will other cpus except 0~15 receive the rx interrupts?
>
>         In our production environment, cpu 16~62 also receive the rx interrupts. Was our RSS misconfigured?

It really depends on which cpus are assigned to each IRQ.

Look at /proc/irq/{IRQ_NUM}/smp_affinity

Also you can have some details in Documentation/networking/scaling.rst