crypto accelerators

[Sam Leffler]

Mike Tancsa wrote:
> On Mon, 17 Apr 2006 16:44:38 -1000 (HST), in sentex.lists.freebsd.net
> you wrote:
> 
>> I've read here before (or maybe some other freebsd list) that cards
>> like the Soekris 1401 don't gain as much as you'd expect due to moving
>> packets to/from the card over the PCI bus.  But the context is usually
>> one of trying to encrypt packets to increase throughput.
>>
>> So the question is whether these cards, regardless of their affect on
>> throughput, increase usable CPU cycles?  I have several Soekris 1401
>> cards and am wondering if there would be any point to putting them
>> into some machines that provide logins over ssh.  These machines are
>> generally pretty good spec, 2.4GHz+, 1GB RAM, Intel MBs, mostly
>> on-board peripherals.
> 
> 
> The only place I found it really helpful for ssh connections was on
> our backup server where we had multiple inbound ssh connections (e.g.
> 10+ at once sending dump piped through ssh) it kept the CPU
> utilization down.  If you have just one or two, it doesnt really
> matter

Unless you're doing lots of scp's it's unlikely ssh traffic is going to 
generate large packets so offloading the crypto won't be worthwhile 
(cost to setup the h/w op probably is higher than doing the op in s/w). 
  This has been discussed previously; see for example my BSDCan 2003 paper.

	Sam