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

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Message-ID: <aFATYATliil63D5R@lore-desk>
Date: Mon, 16 Jun 2025 14:51:44 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Eric Dumazet <edumazet@...gle.com>, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	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 Thu, 12 Jun 2025 23:02:30 +0200 Lorenzo Bianconi wrote:
> > > I'm not Eric but FWIW 256B is not going to help much. It's best to keep
> > > the len / truesize ratio above 50%, so with 32k buffers we're talking
> > > about copying multiple frames.  
> > 
> > what I mean here is reallocate the skb if the true size is small (e.g. below
> > 256B) in order to avoid consuming the high order page from the page_pool. Maybe
> > we can avoid it if reducing the page order to 2 for LRO queues provide
> > comparable results.
> 
> Hm, truesize is the buffer size, right? If the driver allocated n bytes
> of memory for packets it sent up the stack, the truesizes of the skbs
> it generated must add up to approximately n bytes.

With 'truesize' I am referring to the real data size contained in the x-order
page returned by the hw. If this size is small, I was thinking to just allocate
a skb for it, copy the data from the x-order page into it and re-insert the
x-order page into the page_pool running page_pool_put_full_page().
Let me do some tests with order-2 page to see if the GRO can compensate the
reduced page size.

Regards,
Lorenzo

> 
> So if the HW places one aggregation session per buffer, and the buffer
> is 32kB -- to avoid mem use ratio < 25% you'd need to copy all sessions
> smaller than 8kB?
> 
> If I'm not making sense - just ignore, I haven't looked at the rest of
> the driver :)
> 

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