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Can't get Samba/CIFS smbd process to run at more than 10% CPU when testing with NetBench

Iain Soedring
Occasional Advisor

Can't get Samba/CIFS smbd process to run at more than 10% CPU when testing with NetBench

I'm running some NetBench tests of a HP UX V3 Itanium. When configuring NetBench to run at maximum load on 4 clients I'm unable to get more than 80Mbps throughput.
During these test runs my CPU is at about 40% occupancy, disk util 30%, Mem util 50%, Network Util 20%.
So it looks like the bottleneck isn't hardware related, and I've verified that my NetBench clients aren't maxing-out their CPUs.
Where could the bottleneck be?
One thing I've noticed is that the smbd processes never get above 10.5% cpu occupancy, averaging around 9% during the test runs. Could Samba/CIFS be the culprit? I've configured according the docs, setting the kernel params appropriately.
2 REPLIES
Steven E. Protter
Exalted Contributor

Re: Can't get Samba/CIFS smbd process to run at more than 10% CPU when testing with NetBench

Shalom,

http://www.hpux.ws/?p=6

Samba is I/O intensive, not CPU intensive.

You would need to open up a lot of samba sessions to push CPU use for the samba as a whole very high.

Note, you are never going to get the theoretical maximum throughput of the disks you are using in real life.

In real life the systems you do significantly less than theorical maximum. What Mbs are you expecting? What kind of storage are we talking about.

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Steven E Protter
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eric roseme
Respected Contributor

Re: Can't get Samba/CIFS smbd process to run at more than 10% CPU when testing with NetBench

Back in 2001 I wrote these sizing guidelines for CIFS Server:

http://www.docs.hp.com/en/4500/CIFS_Sizing_Final_v102.pdf

Obviously the entire test platform is obsolete now, but there was no problem to drive CIFS to 100% CPU, it was just a function of how many client processes to start. But 80Mbps at 10% CPU is pretty good!

You can also look at this tuning presentation from 2003 - oops, it's not on the external website. Most of the data in there is still valid, except these days the socket options have no effect, so there is no use in tweaking them. Anyway, Samba can make a lot of work for itself with stat-ing directories and messing with locking. It's best to set up your smb.conf for minimal meta-data processing. You can email me and I'll send you the .ppt file if you want it. Just use my name and hp dot com.

Eric Roseme