Subject: Re: [PATCH 4/4 V2 net-next] net: mana: Assigning IRQ affinity on HT cores

From: Yury Norov <[email-masked]>
Date: Wed, 24 Jan 2024 07:20:27 -0800

On Mon, Jan 22, 2024 at 08:00:59AM -0800, Souradeep Chakrabarti wrote:
> Existing MANA design assigns IRQ to every CPU, including sibling
> hyper-threads. This may cause multiple IRQs to be active simultaneously
> in the same core and may reduce the network performance.
> 
> Improve the performance by assigning IRQ to non sibling CPUs in local
> NUMA node. The performance improvement we are getting using ntttcp with
> following patch is around 15 percent against existing design and
> approximately 11 percent, when trying to assign one IRQ in each core
> across NUMA nodes, if enough cores are present.
> The change will improve the performance for the system
> with high number of CPU, where number of CPUs in a node is more than
> 64 CPUs. Nodes with 64 CPUs or less than 64 CPUs will not be affected
> by this change.
> 
> The performance study was done using ntttcp tool in Azure.
> The node had 2 nodes with 32 cores each, total 128 vCPU and number of channels
> were 32 for 32 RX rings.
> 
> The below table shows a comparison between existing design and new
> design:
> 
> IRQ   node-num    core-num   CPU        performance(%)
> 1      0 | 0       0 | 0     0 | 0-1     0
> 2      0 | 0       0 | 1     1 | 2-3     3
> 3      0 | 0       1 | 2     2 | 4-5     10
> 4      0 | 0       1 | 3     3 | 6-7     15
> 5      0 | 0       2 | 4     4 | 8-9     15
> ---
> ---
> 25     0 | 0       12| 24    24| 48-49   12
> ---
> 32     0 | 0       15| 31    31| 62-63   12
> 33     0 | 0       16| 0     32| 0-1     10
> ---
> 64     0 | 0       31| 31    63| 62-63   0

Did that omitted lines mean 5-24 : 15%, 25-31 : 12% and 33-63 : 10%?
Or that means that you didn't test those?

Would be nice to have full coverage...

Thanks,
Yury