netdev - Re: TCP-MD5 checksum failure on x86

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Message-Id: <20100516.003045.146327908.davem@davemloft.net>
Date:	Sun, 16 May 2010 00:30:45 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	shemminger@...tta.com
Cc:	eric.dumazet@...il.com, bhaskie@...il.com,
	bhutchings@...arflare.com, netdev@...r.kernel.org
Subject: Re: TCP-MD5 checksum failure on x86_64 SMP

From: Stephen Hemminger <shemminger@...tta.com>
Date: Fri, 7 May 2010 10:36:39 -0700

> On Fri, 07 May 2010 19:21:33 +0200
> Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
>> Le vendredi 07 mai 2010 à 10:14 -0700, Stephen Hemminger a écrit :
>> 
>> > Forget the per cpu data; the pool should just be scrapped.
>> > 
>> > The only reason the pool exists is that the crypto hash state which
>> > should just be moved into the md5_info (88 bytes).  The pseudo
>> > header can just be generated on the stack before passing to the crypto
>> > code.
>> 
>> 
>> Sure, but I'm afraid there is no generic API do do that (if we want to
>> reuse crypto/md5.c code).
> 
> It looks like the pool is just an optimization to avoid opening too
> many crypto API connections.  This should only be an issue if offloading
> MD5.

It's an issue because creating a crypto API context is expensive, so this
influences our connection rates with MD5.
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