netdev - Re: [PATCH net-next] net: airoha: Add TCP LRO support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aEg1lvstEFgiZST1@lore-rh-laptop>
Date: Tue, 10 Jun 2025 15:39:34 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: airoha: Add TCP LRO support

On Jun 10, Eric Dumazet wrote:
> On Tue, Jun 10, 2025 at 2:12 AM Lorenzo Bianconi <lorenzo@...nel.org> wrote:
> >
[...]
> > @@ -767,7 +887,7 @@ static int airoha_qdma_init_rx_queue(struct airoha_queue *q,
> >         int qid = q - &qdma->q_rx[0], thr;
> >         dma_addr_t dma_addr;
> >
> > -       q->buf_size = PAGE_SIZE / 2;
> > +       q->buf_size = pp_params.max_len / (2 * (1 + lro_queue));
> 
> Tell us more... It seems small LRO packets will consume a lot of
> space, incurring a small skb->len/skb->truesize ratio, and bad TCP WAN
> performance.

I think the main idea is forward to hw LRO queues (queues 24-31 in this
case) just specific protocols with mostly big packets but I completely
agree we have an issue for small packets. One possible approach would be
to define a threshold (e.g. 256B) and allocate a buffer or page from the
page allocator for small packets (something similar to what mt7601u driver
is doing[0]).  What do you think?

> 
> And order-5 pages are unlikely to be available in the long run anyway.

I agree. I guess we can reduce the order to ~ 2 (something similar to
mtk_eth_soc hw LRO implementation [1]).

> 
> LRO support would only make sense if the NIC is able to use multiple
> order-0 pages to store the payload.

The hw supports splitting big packets over multiple order-0 pages if we
increase the MTU over one page size, but according to my understanding
hw LRO requires contiguous memory to work.

Regards,
Lorenzo

[0] https://github.com/torvalds/linux/blob/master/drivers/net/wireless/mediatek/mt7601u/dma.c#L146
[1] https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/mediatek/mtk_eth_soc.c#L2258

Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)