netdev - Re: Question about TPA/HDS feature of bnxt

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Message-ID: <CACKFLimwA=P4M8UEW5cKgnCMCRu99d5DBX17O6ERriUkC=NxMA@mail.gmail.com>
Date: Tue, 13 Aug 2024 19:08:06 -0700
From: Michael Chan <michael.chan@...adcom.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Taehee Yoo <ap420073@...il.com>, David Wei <dw@...idwei.uk>, 
	Somnath Kotur <somnath.kotur@...adcom.com>, Mina Almasry <almasrymina@...gle.com>, 
	Netdev <netdev@...r.kernel.org>
Subject: Re: Question about TPA/HDS feature of bnxt_en

On Tue, Aug 13, 2024 at 6:17 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 13 Aug 2024 19:42:51 +0900 Taehee Yoo wrote:
> > Hi,
> > I'm currently testing the device memory TCP feature with the bnxt_en
> > driver because Broadcom NICs support TPA/HDS, which is a mandatory
> > feature for the devmem TCP.
> > But it doesn't work for short-sized packets(under 300?)
> > So, the devmem TCP stops or errors out if it receives non-header-splitted skb.
> >
> > I hope the bnxt_en driver or firmware has options that force TPA to
> > work for short-sized packets.
> > So, Can I get any condition information on TPA?
>
> I don't have any non-public info but look around the driver for
> rx_copy_thresh, it seems to be sent to FW.
>

Yes, the rx_copy_thresh is also the HDS threshold.  The default value
is 256, meaning that packet sizes below 256 will not be split.  So a
300-byte packet should be split.

TPA is related but is separate.  There is a min_agg_len that is
currently set to 512 in bnxt_hwrm_vnic_set_tpa().  I think it should
be fine to reduce this value for TPA to work on smaller packets.

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