Re: [PATCH net-next v5 0/2] net: mana: add ethtool private flag for full-page RX buffers

[Dipayaan Roy]

On Tue, Apr 07, 2026 at 03:10:45PM +0200, Alexander Lobakin wrote:
> From: Dipayaan Roy <dipayanroy@xxxxxxxxxxxxxxxxxxx>
> Date: Sat, 4 Apr 2026 20:42:15 -0700
> 
> > 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
> 
> Sorry I may've missed the previous threads.
> 
> Has this approach been discussed here? Private flags are generally
> discouraged.
> 
> Alternatively, you can provide Ethtool ops to change the Rx buffer size,
> so that you'd be able to set it to PAGE_SIZE on affected platforms and
> the result would be the same.
>
Hi Alex, 
This was discussed here:
https://lore.kernel.org/all/adHTm2SvjDrezEdv@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ 
> > 
> > There is no behavioral change by default. The flag can be persisted
> > via udev rule for affected platforms.
> > 
> > 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    | 164 ++++++++++++++----
> >  include/net/mana/mana.h                       |   8 +
> >  3 files changed, 163 insertions(+), 31 deletions(-)
> 
> Thanks,
> Olek