Eliminating gettimeofday from construct_reply

Steven French sfrench at us.ibm.com
Thu Aug 1 07:21:01 GMT 2002

>Pardon my skepticism, but is there any evidence that calling gettimeofday
>from this location in the code is actually contributing in any material
>to the performance of Samba?  Any measurements?

Yes, Andrew Theurer had done profiling of various netbench runs and
gettimeofday was one of the unexpected hot spots that showed up in the top
ten on the samples although of course the copy routines were hit even more
often.   Reducing its use (so it is not called on every smb reply) would
not lead to a huge performance improvement but I would expect its impact to
be measurable,  perhaps a few percent improvement.

The performance and scalability teams in the IBM LTC (which Andrew Theurer
is in), although mostly with the goal of optimizing the kernel performance,
seem to have learned a fair amount about the applications like Samba that
the benchmarks they run (including Netbench).     If I had more time I also
would like to work with them more to see if there are easy protocol related
enhancements that would measurablly help performance that we could propose
to the Technical Workgroup for optional extensions (using e.g. Richard's
netbench simulator or one of the VFS clients to experiment).

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

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