High SFTP CPU usage

In my experience, lftp using sftp or fish uses a lot of CPU.  (That's as 
shown by top -- i'm not counting time spent in ssh).  Sending a large 
(hundreds of megabytes) file over a 100Mbps LAN I get 8-10 MBps, with 
about 35% user time in ssh.  The problem is that there's another 20% or 
so in lftp.  (openssh's sftp, on the other hand, uses under 2%.)  This 
system is an Athlon 64 3200+ (running 32-bit); this CPU usage isn't a 
huge problem, but it is for a slower computer.

I've attached a profile, in case that helps.  (The profiled version took 
more like 30% CPU).  It looks like very little of the time is spent in 
the SFTP code.

This is lftp 3.0.3 from atrpms.  I have similar results when I build it 
myself with -O3.  I'm running Fedora development with a stock 
2.6.6-rc2-mm1 kernel and the natsemi driver if that matters.

Anything else I can do to help?

Thanks,
Andy