netdev - Re: [Intel-wired-lan] [PATCH net 0/5] idpf: replace Tx flow scheduling buffer ring with buffer pool

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Message-ID: <c6444d15-bc20-41a8-9230-9bb266cb2ac6@molgen.mpg.de>
Date: Mon, 30 Jun 2025 18:22:11 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Joshua A Hay <joshua.a.hay@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: Re: [Intel-wired-lan] [PATCH net 0/5] idpf: replace Tx flow
 scheduling buffer ring with buffer pool

Dear Josh,


Am 30.06.25 um 18:08 schrieb Hay, Joshua A:

>> Am 25.06.25 um 18:11 schrieb Joshua Hay:
>>> This series fixes a stability issue in the flow scheduling Tx send/clean
>>> path that results in a Tx timeout.
>>>
>>> The existing guardrails in the Tx path were not sufficient to prevent
>>> the driver from reusing completion tags that were still in flight (held
>>> by the HW).  This collision would cause the driver to erroneously clean
>>> the wrong packet thus leaving the descriptor ring in a bad state.
>>>
>>> The main point of this refactor is replace the flow scheduling buffer
>>
>> … to replace …?
> 
> Thanks, will fix in v2
> 
>>> ring with a large pool/array of buffers.  The completion tag then simply
>>> is the index into this array.  The driver tracks the free tags and pulls
>>> the next free one from a refillq.  The cleaning routines simply use the
>>> completion tag from the completion descriptor to index into the array to
>>> quickly find the buffers to clean.
>>>
>>> All of the code to support the refactor is added first to ensure traffic
>>> still passes with each patch.  The final patch then removes all of the
>>> obsolete stashing code.
>>
>> Do you have reproducers for the issue?
> 
> This issue cannot be reproduced without the customer specific device
> configuration, but it can impact any traffic once in place.

Interesting. Then it’d be great if you could describe that setup in more 
detail.

>>> Joshua Hay (5):
>>>     idpf: add support for Tx refillqs in flow scheduling mode
>>>     idpf: improve when to set RE bit logic
>>>     idpf: replace flow scheduling buffer ring with buffer pool
>>>     idpf: stop Tx if there are insufficient buffer resources
>>>     idpf: remove obsolete stashing code
>>>
>>>    .../ethernet/intel/idpf/idpf_singleq_txrx.c   |   6 +-
>>>    drivers/net/ethernet/intel/idpf/idpf_txrx.c   | 626 ++++++------------
>>>    drivers/net/ethernet/intel/idpf/idpf_txrx.h   |  76 +--
>>>    3 files changed, 239 insertions(+), 469 deletions(-)


Kind regards,

Paul