Subject: Re: 25%+ improvement in in_cksum speed!
To: Michael Graff <explorer@flame.org>
From: Steven M. Bellovin <smb@research.att.com>
List: port-i386
Date: 09/17/2002 20:18:27
In message <v6admgrw60.fsf@kechara.flame.org>, Michael Graff writes:
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>"Steven M. Bellovin" <smb@research.att.com> writes:
>
>> I haven't looked at your code in detail, but how does it perform on 
>> small packets?  (~40-50% of packets are about 40 bytes.)
>
>It's not my code, but here's what happens when I use a size of 50
>bytes:
>
>          in_cksum.s sum a26d took     2887 usecs 0.563867 nsec/byte
>           asm adc 1 sum eab6 took     5033 usecs 0.983008 nsec/byte
>          asm adc 1a sum eab6 took     3758 usecs 0.733984 nsec/byte
>Segmentation fault (core dumped)
>
>
>:)
>

Ignoring the segfaul for now, those numbers suggest that we need the 
current code for small blocks and one of the newer ones for long 
bloocks.

		--Steve Bellovin, http://www.research.att.com/~smb (me)
		http://www.wilyhacker.com ("Firewalls" book)