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Date: Thu, 2 Jan 2025 08:39:15 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Edward Cree <ecree.xilinx@gmail.com>
Cc: Haifeng Xu <haifeng.xu@shopee.com>, Eric Dumazet <edumazet@google.com>,
 Tony Nguyen <anthony.l.nguyen@intel.com>, Przemek Kitszel
 <przemyslaw.kitszel@intel.com>, "David S. Miller" <davem@davemloft.net>,
 Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org,
 netdev@vger.kernel.org, intel-wired-lan@lists.osuosl.org
Subject: Re: [Question] =?UTF-8?B?aXhnYmXvvJpNZWNoYW5pc20=?= of RSS
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On Thu, 2 Jan 2025 16:01:18 +0000 Edward Cree wrote:
> On 02/01/2025 11:23, Haifeng Xu wrote:
> > We want to make full use of cpu resources to receive packets. So
> > we enable 63 rx queues. But we found the rate of interrupt growth
> > on cpu 0~15 is faster than other cpus(almost twice).  
> ...
> > I am confused that why ixgbe NIC can dispatch the packets
> > to the rx queues that not specified in RSS configuration.  
> 
> Hypothesis: it isn't doing so, RX is only happening on cpus (and
>  queues) 0-15, but the other CPUs are still sending traffic and
>  thus getting TX completion interrupts from their TX queues.
> `ethtool -S` output has per-queue traffic stats which should
>  confirm this.
> 
> (But Eric is right that if you _want_ RX to use every CPU you
>  should just change the indirection table.)

IIRC Niantic had 4 bit entries in the RSS table or some such.
It wasn't possible to RSS across more than 16 queues at a time.
It's a great NIC but a bit dated at this point.