Samba performance problem over a radio link.
David.Collier-Brown at canada.sun.com
Thu Jun 8 15:31:17 GMT 2000
| We have a performance problem over a 2 Mbits radio link.
>From your message, it looks like this is what you have, in
the same units: please correct me if this isn't right, as
I'm really reduced to guessing from your description...
Description KB/S Kbit/S Mbits/S % of max
Theoretical Max. 100 Mbit/S Eth. 12500 100000 100 100
local smb read, win9x 5000 40000 40 40
local smb read, win9x to NT server 160 1280 1.28 1.28
This can't be true...
Theoretical Maximum, 2Mbit/S radio 250 2000 2 100
remote smb read, win9x 70 560 0.56 28
remote ftp read, win9x 100 800 0.8 40
remote smb read, NT 100 800 0.8 40
This looks plausible.
I'm going to assume you want to know why Samba
with win9x clients is slower than ftp and NT clients
over the speed-limited link.
I **think** that the win9x SMB client program is not
as good as packing lots of no-response-required
operations into packets as the NT SMB client, and this
shows up strongly on the speed-limited network. The
client send a request, and starts waiting for an ACK.
This is called "stop-wait" processing, for obvious
reasons (;-)) The desired behavior is to send a bunch
of requests and never wait.
Playing with the receive window will allow the sender to
send as many packets, containing SMBs, as possible, but the
SMB protocol can defeat this. I suspect that's why the
improvement from playing with rwin levels off suddenly.
TCP gurus, do please chime in!
I think you might try two experiments: tuning the TCP for
large file throughput (normally not recommended) and turning
off raw read/write (ditto).
In three separate experiments, try
read raw = no
write raw = no
socket options = TCP_THROUGHPUT IPTOS_THROUGHPUT
If any causes a significant improvement, please tell
the list: these are contra-intuitive approaches...
Once we're past this, we'll look at SO_SNDBUF= with large values.
David Collier-Brown, | Always do right. This will gratify some people
185 Ellerslie Ave., | and astonish the rest. -- Mark Twain
Willowdale, Ontario | //www.oreilly.com/catalog/samba/author.html
Work: (905) 415-2849 Home: (416) 223-8968 Email: davecb at canada.sun.com
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