netdev - Re: [RFC PATCH 0/3] Simplified 16 bit Toeplitz hash algorithm

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Date:	Mon, 3 Jan 2011 10:47:20 -0800
From:	Tom Herbert <therbert@...gle.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] Simplified 16 bit Toeplitz hash algorithm

I'm not sure why this would be needed.  What is the a advantage in
making the TX and RX queues match?

On Fri, Dec 17, 2010 at 5:00 PM, Alexander Duyck
<alexander.h.duyck@...el.com> wrote:
> This patch series is meant to be a proof of concept for simplifying the cost
> of Toeplitz hashing by reducing the complexity of the key to a 16 bit
> repeating value.  The resultant advantages are that the hash computation
> performance is significantly increased, and that the resultant hash is the
> same for flows in either direction.
>
> The idea for this occurred to me while working on the ATR hashing algorithms
> and improving their performance.  ATR implements a 32 bit repeating key which
> results in us being able to XOR everything down to a 32 bit value.  By using a
> 16 bit key we are able to cut down the 12 to 36 byte input value to only 2
> bytes via XOR operations.  This reduces the resultant hash to 16 bits, however
> since queue selection only requires 7 bits for RSS that still leaves us with a
> large enough resultant key.
>
> I'm currently not planning to do any more work on this in the near future as I
> have several other projects in which I am currently engaged.  However I just
> wanted to put this code out there in case anyone had a use for it.
>
> Thanks,
>
> Alex
>
> ---
>
> Alexander Duyck (3):
>      igb: example of how to update igb to make use of in-kernel Toeplitz hashing
>      ixgbe: example of how to update ixgbe to make use of in-kernel Toeplitz hash
>      net: add simplified 16 bit Toeplitz hash function for transmit side hashing
>
>
>  drivers/net/igb/igb_main.c     |   22 ++++------
>  drivers/net/ixgbe/ixgbe_main.c |   47 ++++++++++++---------
>  include/linux/netdevice.h      |    2 +
>  include/linux/toeplitz.h       |   89 ++++++++++++++++++++++++++++++++++++++++
>  net/core/dev.c                 |   68 +++++++++++++++++++++++++++++++
>  5 files changed, 195 insertions(+), 33 deletions(-)
>  create mode 100644 include/linux/toeplitz.h
>
> --
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