netdev - RE: [PATCH net-next] hyperv: Add support for Virtual Receive Side Scaling (vRSS)

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Message-ID: <05be4f23ff784e56b710dd02eb88358a@DFM-DB3MBX15-08.exchange.corp.microsoft.com>
Date:	Thu, 19 Dec 2013 20:49:42 +0000
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	Tom Herbert <therbert@...gle.com>
CC:	Daniel Borkmann <dborkman@...hat.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	KY Srinivasan <kys@...rosoft.com>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>
Subject: RE: [PATCH net-next] hyperv: Add support for Virtual Receive Side
 Scaling (vRSS)



> -----Original Message-----
> From: Tom Herbert [mailto:therbert@...gle.com]
> Sent: Thursday, December 19, 2013 2:59 PM
> To: Haiyang Zhang
> Cc: Daniel Borkmann; Ben Hutchings; davem@...emloft.net;
> netdev@...r.kernel.org; KY Srinivasan; olaf@...fle.de;
> jasowang@...hat.com; linux-kernel@...r.kernel.org; driverdev-
> devel@...uxdriverproject.org
> Subject: Re: [PATCH net-next] hyperv: Add support for Virtual Receive Side
> Scaling (vRSS)
> 
> I posted an implementation of library functions for Toeplitz (see [PATCH 1/2]
> net: Toeplitz library functions).  This includes some pre-computation of the
> table to get reasonable performance in the host. Please take a look.
> 
> On the other hand, if you're computing a hash in the host, do you really need
> Toeplitz, flow_dissector already supports a good hash computation and can
> parse many more packets than just plain UDP/TCP.
> We probably only should be doing Toeplitz in the host if we need to match
> HW computed values.

The Hyper-V host requires the guest to select channel based on Toeplitz hash, so
we need to compute it on the guest. 

Regarding the Toeplitz function, do you mean this patch?
http://patchwork.ozlabs.org/patch/277344/
This doesn't contain the implementation. Could you point me to the actual code?

Thanks,
- Haiyang