[Samba] SMBD CPU climbs sky high when writing DPX files

Volker Lendecke Volker.Lendecke at SerNet.DE
Thu Nov 5 13:20:24 MST 2009

On Thu, Nov 05, 2009 at 01:43:59PM -0500, Andy Liebman wrote:
> >The problem is the following: When creating a file we have
> >to prove that the file does not exist in a different
> >upper/lower case combination. Under Unix, the only way to
> >prove this is to list the whole directory and do a case
> >insensitive comparison on each existing file.
> >
> >  
> Thank you SO much. Your suggestion totally solved the problem. It makes 
> sense when you think about it.
> Results:  When capturing standard definition DPX files, CPU utilization 
> is now down at 7 percent (out of 400 percent) and holds steady forever 
> basically.  I was able to capture 150,000 frames (83 minutes) before I 
> got bored and stopped my test. 
> In addition, I'm now capturing HD-444 DPX files which run at about 260 
> MB/sec and that's doing fine as well -- running at 37 percent total CPU 
> (out of 400 percent).

If you want to read them out at wire speed, you might want
to look at the vfs_preopen module, part of Samba 3.4. In
case you have latency problems, this module forks helper
processes that open and read the next n files in sequence.
It was written for exactly your application, out of a
cluster file system with pretty high open latency we got
almost 400MBytes/second with that module well tuned,
regardless of the broken access pattern :-)

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