netdev - Re: [PATCH net-next] net: ovs: use CRC32 accelerated flow hash if available

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Message-ID: <CA+mtBx_FPUf=K=tBKmwe8-r7OsgiMS8VE6bYpyQa+OY7Cn=MaQ@mail.gmail.com>
Date:	Tue, 10 Dec 2013 13:27:28 -0800
From:	Tom Herbert <therbert@...gle.com>
To:	David Miller <davem@...emloft.net>
Cc:	Jesse Gross <jesse@...ira.com>, ffusco@...hat.com,
	Linux Netdev List <netdev@...r.kernel.org>,
	dev@...nvswitch.org, Daniel Borkmann <dborkman@...hat.com>,
	tgraf@...hat.com
Subject: Re: [PATCH net-next] net: ovs: use CRC32 accelerated flow hash if available

On Tue, Dec 10, 2013 at 11:36 AM, David Miller <davem@...emloft.net> wrote:
> From: Jesse Gross <jesse@...ira.com>
> Date: Tue, 10 Dec 2013 11:28:08 -0800
>
>> I think this is definitely a good optimization to do given that so
>> much of the work that OVS does is hashing. However, isn't there a
>> library where there would be a more appropriate place to put this?
>
> I also honestly don't see why we want to special case OVS at all
> here.  This faster hashing would be useful for socket demux and
> other locations in the kernel.
>

Also, we already do a lot of work to compute flow hashes for packets
in both TX and RX.  Can these be leveraged? For instance, if OVS is
computing a 5-tuple hash on an RX packet it's probably redundant to
skb->rxhash.

> When I see changes like this my only reaction is "sad face".
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