Re: [PATCH] net/core/flow.c: compare data with memcmp

[Daniel Marjamäki]

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@xxxxxxxxxxxxx>:
> From: "Daniel_Marjamäki" <daniel.marjamaki@xxxxxxxxx>
> 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@xxxxxxxxx>
>
> 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.
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