Windows XP vs Samba and asynchronous IO

James Roper u3205097 at
Sat Apr 9 00:53:08 GMT 2005

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 Roper
u3205097 at
Phone: +61 2 9524 3380      Mobile: +61 438 406 331

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