[Samba] Vista client / Linux server - high browsing latency

Marcello Romani mromani at ottotecnica.com
Tue Jun 12 06:22:15 GMT 2007

Jay L. T. Cornwall ha scritto:
> Hash: SHA1
> Aravinda Guzzar wrote:
>> You can do the similar tracing on the client side using
>> ethereal/wireshark. Filter out for smb packets and see which smb
>> request/response is taking maximum time, to track down the problem.
> Thanks for the tip. I did a packet capture when the share was working
> quickly and when it had slowed down again following a reboot.
> Now I'm a bit confused. Both traces show roughly the same number of
> packets and the server response time is about the same in both cases
> (somewhere between 0.1 and 0.2ms on average). However in the slower
> trace, the time between the client receiving a response and sending its
> next request is much larger - about 15ms versus 0.2ms.
> It would appear, then, that the Samba server isn't at fault. The client
> is experiencing long delays between submitting requests; which seems to
> fix itself following some pattern of usage that I haven't yet figured out.
> How weird. :S
> - --
> Jay L. T. Cornwall, http://www.esuna.co.uk/~jay/
> PhD Student
> Imperial College London
> Version: GnuPG v1.4.7 (MingW32)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
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> Z1vMPGhDZWVnQIPvW1jRaqg=
> =afsD

I had a performance problem that was related to how the XP tcp/ip stack
manages ack packets. Maybe what I'm going to say is relevant to Vista, too ?

My client is Windows XP SP2, my server is Gentoo Linux running samba
3.0.22, network is 100Mbit on the client, 1Gbit on the server. The share
is mapped as drive K:, and is mounted on a couple of 10K rpm U160 scsi
drives (software raid-1).
Client PC has 1GB of ram, the server 2GB.

I never had performance problems on my client machine wrt. network
transfers. One day I noticed that accessing data on the network share
was terribly slow; the throughput dropped to about 200-300KB per second
max., while it usually reached 8-9MB/s while copying large files.
 From that day the performance has not increased no matter how many
times  I rebooted the server or the client.
The strange thing is, I'm not the only one using XP SP2 on the same
share, but no one of my colleagues has reported problems to me (I'm the
network admin).

Googling around I found a forum where the following changes in the XP
registry were suggested:

HKLM ==>
   System ==>
     CurrentControlSet ==>
       Services ==>
         Tcpip ==>
           Parameters ==>
             Interfaces ==>
               {network interface GUID} ==>
                  TcpAckFrequency ==> DWORD: 1
                  TcpDelAckTicks  ==> DWORD: 0

I creted the two keys (they were not present), set their values and
rebooted the client machine (no server reboot).
The performance returned to the expected levels, and has been so for
some days now.


Marcello Romani
Responsabile IT
Ottotecnica s.r.l.

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