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Message-ID: <CAADnVQJDxPsMeuNmnR5iUwccOKG2A02dZ+3Ae6wGg-RNFPeeeQ@mail.gmail.com>
Date: Tue, 7 Oct 2014 13:43:09 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: David Miller <davem@...emloft.net>
Cc: Tom Herbert <therbert@...gle.com>, Jesse Gross <jesse@...ira.com>,
"gerlitz.or@...il.com" <gerlitz.or@...il.com>,
Alexander Duyck <alexander.h.duyck@...el.com>,
John Fastabend <john.r.fastabend@...el.com>,
Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Thomas Graf <tgraf@...g.ch>,
Pravin Shelar <pshelar@...ira.com>,
Andy Zhou <azhou@...ira.com>
Subject: Re: [PATCH] net: Add ndo_gso_check
On Tue, Oct 7, 2014 at 1:32 PM, David Miller <davem@...emloft.net> wrote:
> From: Alexei Starovoitov <alexei.starovoitov@...il.com>
> Date: Tue, 7 Oct 2014 13:28:01 -0700
>
>> On Tue, Oct 7, 2014 at 11:47 AM, David Miller <davem@...emloft.net> wrote:
>>>
>>> I am totally against boolean "yes/no" protocol specific checksum
>>> validation by HW.
>>>
>>> It's not faster. You have to look at the pseudo-header and bring it into
>>> the CPU cache _anyways_, so negating it and 2's complementing it into
>>> the CHECKSUM_COMPLETE value for validation is free.
>>>
>>> There is no performance advantage whatsoever to use another checksumming
>>> scheme.
>>
>> ok, forget faster/slower argument for a second.
>> Why is it a bad thing to have HW verifying checksums?
>
> Because you have to change the damn hardware and/or firmware for every
> new protocol.
It is true for existing NICs, but it is not true for upcoming devices.
They're exposing packet parsers to users, so we will be able to
program any protocol into the device without reflashing it.
Some of the guys are even allowing reprogramming the parser
while packets are flowing.
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