netdev - Re: [PATCH v2 net-next 4/4] ibmvnic: Make max subcrq indirect entries tunable via module param

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Message-ID: <20250704170548.GM41770@horms.kernel.org>
Date: Fri, 4 Jul 2025 18:05:48 +0100
From: Simon Horman <horms@...nel.org>
To: Mingming Cao <mmc@...ux.ibm.com>
Cc: netdev@...r.kernel.org, bjking1@...ux.ibm.com, haren@...ux.ibm.com,
	ricklind@...ux.ibm.com, davemarq@...ux.ibm.com
Subject: Re: [PATCH v2 net-next 4/4] ibmvnic: Make max subcrq indirect
 entries tunable via module param

On Wed, Jul 02, 2025 at 10:18:04AM -0700, Mingming Cao wrote:
> This patch increases the default number of subcrq indirect entries from 16
> to 128, a value supported on POWER9 and later systems. Increasing this limit
> improves batching efficiency in hypervisor communication, enhancing throughput
> under high-load conditions.
> 
> To maintain compatibility with older or constrained systems (e.g., some POWER8 platforms),
>  a module parameter max_subcrq_indirect is introduced as a transitional mechanism.
> This allows administrators to manually reduce the limit if needed.
> 
> The module parameter is not intended for dynamic runtime tuning, but rather
> provides forward compatibility without requiring broader structural changes at this time.
> 
> Signed-off-by: Mingming Cao <mmc@...ux.ibm.com>
> Reviewed by: Rick Lindsley <ricklind@...ux.ibm.com>
> Reviewed by: Dave Marquardt <davemarq@...ux.ibm.com>
> Reviewed by: Brian King <bjking1@...ux.ibm.com>
> Reviewed by: Haren Myneni <haren@...ux.ibm.com>

Hi,

In his review of v1 of this patchset, Jakub said:

  Module parameters are strongly discouraged. Please provide more details
  about what this parameter does, I supposed it should be mapped to on of
  the ethtool -g options.

  https://lore.kernel.org/netdev/20250701183107.6f6411c1@kernel.org/

Perhaps I'm missing something, but I don't see this discussed or addressed.

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