Windows XP vs Samba and asynchronous IO

[James Roper]

Hey guys,

I've been doing some experimentation with asynchronous read routines in 
the Linux CIFS VFS client.  I've come across some interesting things 
when comparying Windows XP to Samba that I thought you guys might be 
able to explain.

When I first did my tests, I was copying a 173MB file from my laptop to 
my desktop, they were linked directly with a crossover cable on a 100mb 
network and had a 0.2 millisecond ping time.  My laptop was running 
Linux 2.6 with Samba 3.  These are my results:
Test *      Trial 1     Trial 2     Trial 3    Average
Async      19.711      19.723      18.977      19.470
Sync        21.809      21.105      21.033      21.315
So there was about a 7-8% speed up.  Since then, the harddrive on my 
laptop died, so I replaced the harddrive and installed Windows XP on 
it.  It now has a 0.5 millisecond ping time in the same environment.  
So, doing the same test, I find that using synchronous read routines 
it's averaging about 1 minute 10 seconds, and with asynchronous routines 
it's averaging 24 seconds, a 60-70% speed up.  Does this sound 
right/surprise you at all?  My guess is that the Windows XP network 
stack is very slow, it can handle high bandwidths but has a really high 
latency.  Any other explainations?

James

-- 
James Roper
u3205097 at alumni.anu.edu.au
Phone: +61 2 9524 3380      Mobile: +61 438 406 331