netdev - Re: [PATCH net-next] ibmvnic: Toggle between queue types in affinity mapping

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Date:   Wed, 25 Jan 2023 10:55:20 -0600
From:   Nick Child <nnac123@...ux.ibm.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, bjking1@...ux.ibm.com, haren@...ux.ibm.com,
        ricklind@...ibm.com
Subject: Re: [PATCH net-next] ibmvnic: Toggle between queue types in affinity
 mapping



On 1/24/23 20:39, Jakub Kicinski wrote:
> On Mon, 23 Jan 2023 16:17:27 -0600 Nick Child wrote:
>> A more optimal algorithm would balance the number RX and TX IRQ's across
>> the physical cores. Therefore, to increase performance, distribute RX and
>> TX IRQs across cores by alternating between assigning IRQs for RX and TX
>> queues to CPUs.
>> With a system with 64 CPUs and 32 queues, this results in the following
>> pattern (binding is done in reverse order for readable code):
>>
>> IRQ type |  CPU number
>> -----------------------
>> TX15	 |	0-1
>> RX15	 |	2-3
>> TX14	 |	4-5
>> RX14	 |	6-7
> 
> Seems sensible but why did you invert the order? To save LoC?

Thanks for checking this out Jakub.

Correct, the effect on performance is the same and IMO the algorithm
is more readable. Less so about minimizing lines and more about
making the code understandable for the next dev.