On Fri, 27 Mar 2026 04:00:31 +0000 Long Li wrote:

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  We considered netif_get_num_default_rss_queues() but chose a fixed

default based on our performance testing. On Azure VMs, typical

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  workloads plateau at around 16 queues - adding more queues beyond that

doesn't improve throughput but increases memory usage and

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  interrupt overhead.

  netif_get_num_default_rss_queues() would return 32-64 on large VMs

(64-128 vCPUs), which wastes resources without benefit.

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  That said, I agree that completely ignoring the core-based heuristic isn't

ideal for consistency. One option is to use

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  netif_get_num_default_rss_queues() but clamp it to a maximum of

MANA_DEF_NUM_QUEUES (16), so small VMs still get enough queues and

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  large VMs don't over-allocate. Something like:

   apc->num_queues = min(netif_get_num_default_rss_queues(),

MANA_DEF_NUM_QUEUES);

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   apc->num_queues = min(apc->num_queues, gc->max_num_queues);

  For reference, it seems mlx4 does something similar - it caps at

DEF_RX_RINGS (16) regardless of core count.

mlx4 is a bit ancient. And mlx5 does the wrong thing, which is why I'm so
sensitive to this issue :(

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  Do you want me to send a v2?

Please send a follow up, let's leave this patch be and make an incremental
change.

Thanks!

I will send a follow-up patch.

Thanks,
Long