From: "Daniel Marjamäki" <daniel.marjamaki@gmail.com>
To: "David Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org, kernel-janitors@lists.osdl.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net/core/flow.c: compare data with memcmp
Date: Mon, 1 Jan 2007 08:47:48 +0100 [thread overview]
Message-ID: <80ec54e90612312347w2b906e5eg725a7761110c6897@mail.gmail.com> (raw)
In-Reply-To: <20061231.123715.115911390.davem@davemloft.net>
Hello!
So you mean that in this particular case it's faster with a handcoded
comparison than memcmp? Because both key1 and key2 are located at
word-aligned addresses?
That's fascinating.
Best regards,
Daniel
2006/12/31, David Miller <davem@davemloft.net>:
> From: "Daniel_Marjamäki" <daniel.marjamaki@gmail.com>
> Date: Sun, 31 Dec 2006 17:37:05 +0100
>
> > From: Daniel Marjamäki
> > This has been tested by me.
> > Signed-off-by: Daniel Marjamäki <daniel.marjamaki@gmail.com>
>
> Please do not do this.
>
> memcmp() cannot assume the alignment of the source and
> destination buffers and thus will run more slowly than
> that open-coded comparison.
>
> That code was done like that on purpose because it is
> one of the most critical paths in the networking flow
> cache lookup which runs for every IPSEC packet going
> throught the system.
>
next prev parent reply other threads:[~2007-01-01 7:47 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-31 16:37 Daniel Marjamäki
2006-12-31 19:49 ` [KJ] " Nishanth Aravamudan
2006-12-31 20:37 ` David Miller
2007-01-01 7:47 ` Daniel Marjamäki [this message]
2007-01-01 8:49 ` David Miller
2007-01-01 9:16 ` Daniel Marjamäki
2007-01-02 23:36 ` David Miller
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