Re: [PATCH net-next v11 0/2] net: mana: add ethtool private flag for full-page RX buffers

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

On Wed, Jul 01, 2026 at 07:15:44AM -0700, Dipayaan Roy wrote:
> On some ARM64 platforms with 4K PAGE_SIZE, utilizing page_pool
> fragments for allocation in the RX refill path (~2kB buffer per fragment)
> causes 15-20% throughput regression under high connection counts
> (>16 TCP streams at 180+ Gbps). Using full-page buffers on these
> platforms shows no regression and restores line-rate performance.
> 
> This behavior is observed on a single platform; other platforms
> perform better with page_pool fragments, indicating this is not a
> page_pool issue but platform-specific.
> 
> This series adds an ethtool private flag "full-page-rx" to let the
> user opt in to one RX buffer per page:
> 
>   ethtool --set-priv-flags eth0 full-page-rx on
> 
> There is no behavioral change by default. The flag can be persisted
> via udev rule for affected platforms.

Were you able to track down what is the actual bottleneck on the 'broken'
platform? What is the performance of full-page approach on healthy
platforms? On changelog below you mention the frag approach 'outperforms'
the full-page one.

> 
> This series depends on the following fixes now merged in net-next:
>   commit 17bfe0a8c014 ("net: mana: Add NULL guards in teardown path to prevent panic on attach failure")
>   commit 5b05aa36ee24 ("net: mana: Skip redundant detach on already-detached port")
> 
> Changes in v11:
>   - Rebased on net-next
> Changes in v10:
>   - Rebased on net-next which now includes the prerequisite fixes.
>   - Recovery logic in mana_set_priv_flags() leverages the idempotent
>     mana_detach() from the merged fixes.
> Changes in v9:
>   - Added correct tree.
> Changes in v8:
>   - Fixed queue_reset_work recovery by restoring port_is_up before
>     scheduling reset so the handler can properly re-attach.
>   - Simplified "err && schedule_port_reset" to "schedule_port_reset".
> Changes in v7:
>   - Rebased onto net-next.
>   - Retained private flag approach after David Wei's testing on
>     Grace (ARM64) confirmed that fragment mode outperforms
>     full-page mode on other platforms, validating this is a
>     single-platform workaround rather than a generic issue.
> Changes in v6:
>   - Added missed maintainers.
> Changes in v5:
>   - Split prep refactor into separate patch (patch 1/2)
> Changes in v4:
>   - Dropping the smbios string parsing and add ethtool priv flag
>     to reconfigure the queues with full page rx buffers.
> Changes in v3:
>   - changed u8* to char*
> Changes in v2:
>   - separate reading string index and the string, remove inline.
> 
> Dipayaan Roy (2):
>   net: mana: refactor mana_get_strings() and mana_get_sset_count() to
>     use switch
>   net: mana: force full-page RX buffers via ethtool private flag
> 
>  drivers/net/ethernet/microsoft/mana/mana_en.c |  22 ++-
>  .../ethernet/microsoft/mana/mana_ethtool.c    | 178 +++++++++++++++---
>  include/net/mana/mana.h                       |   8 +
>  3 files changed, 177 insertions(+), 31 deletions(-)
> 
> -- 
> 2.43.0
> 
>