Re: [PATCH net-next 0/4] mpnic: add NAPI buffer depletion check

[Harshitha Ramamurthy]

On Thu, Oct 1, 2026 at 10:35 AM Daniel Zahka <daniel.zahka@xxxxxxxxx> wrote:
>
> This series provides a buffer depletion check to unwedge Rx processing
> when page pool allocations have failed. Patch 4 has a more detailed
> description of the events that lead to the wedge, but the high level
> idea is that when page pool allocations fail, the buffer descriptor ring
> can run low, and when that happens the device will drop Rx packets and
> not raise interrupts, which causes the NAPI event loop not to be
> scheduled, so new buffers are not posted.
>
> There are three setup patches for the depletion check:
>
> Patch 1: convert writes to BDQ ring head and tail to WRITE_ONCE(), so
> the depletion check, which is not synchronized with the NAPI event loop,
> can READ_ONCE() those same fields.
>
> Patch 2: introduce the driver level service task that runs once per
> second while the netif is running.
>
> Patch 3: set the minimum Rx buffers needed per packet based on page size
> and max MTU.
>
> With those in place, we have everything we need to watch the buffer ring
> head and tail positions from the service task, compare posted buffers to
> programmed Rx drop thresholds, and then force mpnic_poll() to run if
> needed.
>
> Signed-off-by: Daniel Zahka <daniel.zahka@xxxxxxxxx>
> ---
> Daniel Zahka (4):
>       eth: mpnic: use WRITE_ONCE() for BDQ head and tail updates
>       eth: mpnic: add a service task
>       eth: mpnic: set Rx buffer minimums using page size and mtu
>       eth: mpnic: add a NAPI depletion check

For the series:
Reviewed-by: Harshitha Ramamurthy <hramamurthy@xxxxxxxxxx>

>
>  drivers/net/ethernet/meta/mpnic/mpnic.h        |  3 +++
>  drivers/net/ethernet/meta/mpnic/mpnic_init.c   | 13 ++++++---
>  drivers/net/ethernet/meta/mpnic/mpnic_netdev.c |  3 +++
>  drivers/net/ethernet/meta/mpnic/mpnic_pci.c    | 21 +++++++++++++++
>  drivers/net/ethernet/meta/mpnic/mpnic_txrx.c   | 37 +++++++++++++++++++++++---
>  drivers/net/ethernet/meta/mpnic/mpnic_txrx.h   |  7 +++++
>  6 files changed, 77 insertions(+), 7 deletions(-)
> ---
> base-commit: eb0c18404c8943356f4aa164e5db9067b79ea93c
> change-id: 20260929-linux-mpnic-428998421ffc
>
> Best regards,
> --
> Daniel Zahka <daniel.zahka@xxxxxxxxx>
>
>