netdev - RE: [PATCH net-next v2 04/12] net: stmmac: Add Split Header support and enable it in XGMAC cores

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Message-ID: <BN8PR12MB3266B9314CF13A9140A72354D3D20@BN8PR12MB3266.namprd12.prod.outlook.com>
Date:   Tue, 13 Aug 2019 08:30:47 +0000
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     David Miller <davem@...emloft.net>,
        "jakub.kicinski@...ronome.com" <jakub.kicinski@...ronome.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next v2 04/12] net: stmmac: Add Split Header support
 and enable it in XGMAC cores

++ Jakub

From: David Miller <davem@...emloft.net>
Date: Aug/12/2019, 22:06:18 (UTC+00:00)

> From: Jose Abreu <Jose.Abreu@...opsys.com>
> Date: Mon, 12 Aug 2019 11:44:03 +0200
> 
> > 	- Add performance info (David)
> 
> Ummm...
> 
> Whilst cpu utilization is interesting, I might be mainly interested in
> how this effects "networking" performance.  I find it very surprising
> that it isn't obvious that this is what I wanted.
> 
> Do you not do performance testing on the networking level when you
> make fundamental changes to how packets are processed by the
> hardware/driver?

I do.

In my HW this feature does not impact performance neither improves it as 
I'm already on max of theoretical bandwidth.

I do expect it to reduce CPU usage and memory footprint because we no 
longer have to memcpy the entire buffer to SKB and instead we just copy 
the header and then append payload as page which is passed directly to 
net layer.

This feature is already used in some drivers and is part of GRO 
offloading I think.

Jakub, as David is off can you please comment on how can we proceed with 
this series ? I can add more information in commit log for this patch 
...

---
Thanks,
Jose Miguel Abreu