Re: [Question] ixgbe：Mechanism of RSS

[Haifeng Xu]

On 2025/1/3 00:39, Jakub Kicinski wrote:
> 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.

Yes, It only has 16 RSS queues.