[ale] sshd resource intensive??

[Geoffrey]

Michael D. Hirsch wrote:
> On Sunday 16 May 2004 09:48 am, Geoffrey wrote:

>>I surely expected some degradation in transmission because of the ssh
>>overhead, but certainly not 8000%.  11 seconds to transfer a 125M file
>>from an athlon 2400+ to pentium IV 2.4G, verses 92 seconds to transfer
>>the same file from the athlon to a PII 350.
>>
>>You learn something new every day..
> 
> 
> Looks like you're on a 100Mbit network and your transfer has maxed out the 
> network.  Since there is a factor of eight slowdown with ssh (800%, not 
> 8000%) you can solve the problem by switching to a 10MBit network.  Both 
> transfers should take about the same time on that network.  :-)

All these machines are on the same 100Mbit network, thus, the 
substantial difference between the transfers noted above must be issues 
with the cpu usage, or poor configuration.  My tests seem to be 
consistent though.  the slower the cpu, the slower the transfer.

> 
> Seriously, I found that over a T1, ssh  would take up a couple of percent of 
> the CPU.  (This was a couple of years ago--it should be less with a modern 
> CPU.)  That does make the numbers you're getting a little higher than I would 
> expect.  At 1% of a CPU for T1 speed, I'd expect 10% at 10-baseT and 100% for 
> 100-baseT.  Seems like our numbers disagree by a factor of 10.

I wouldn't think the cpu usage would vary with the size of the pipe, if 
it did, I'd expect higher usage with a bigger pipe.  With the smaller 
pipe, you'd have it waiting on i/o.

I find the cpu usage to be much higher than 1%.  When transfering a file 
125M file from my athlon 2400 to my PIV 2400 the cpu usage on the 
sending machine was at 35-40% for ssh.  It was comparable on the 
receiving machine.  When sending the same file from the Athlon to a PII 
350 the cpu usage was hovering around 80%.

So our numbers are far different.

-- 
Until later, Geoffrey                     Registered Linux User #108567
Building secure systems in spite of Microsoft