frequency/size distribution of SMBs

Steven French sfrench at
Tue Apr 19 15:29:56 GMT 2005

I want to analyze whether the default small SMB buffer size for the Linux
cifs client, which is currently set at 256 bytes, is reasonable.   The
Linux cifs client has two buffer sizes - the small buffers (which are big
enought to fit some handle based SMB requests and most SMB responses) and a
large SMB buffer size which is the negotiated buffer size (for read
responses, write requests, readdir responses etc.).   For this it would be
helpful to know the % of SMB requests and the % of SMB responses smaller
than various sizes.   What I noticed running the connectathon "nfs" (posix
file API) tests from cifs client to Samba was that increasing the cutoff
from 256 bytes to 1024 bytes changed very little, most SMBs appear to be
either smaller than 256 bytes or much larger (e.g. close to the negotiated
buffer size, or at least bigger than 1K).

Has anyone plotted a frequency distribution of SMBs by size?   This would
be helpful in setting buffer sizes optimally.   I did not see an easy way
to do this in ethereal (it would be easier to code profiling code in smbd
or cifs.ko for this than messing with ethereal it seemed).

Steve French
Senior Software Engineer
Linux Technology Center - IBM Austin
phone: 512-838-2294
email: sfrench at-sign us dot ibm dot com

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