Re: Performance tuning

[Tom McNeal <trmcneal@attbi.com>]

Hi -

I gleaned that tuning info from the SPECsfs and SPECweb99 
benchmarks, and documented it on the Mission Critical Linux
servers that are still kept on line:
http://www.missioncriticallinux.com/orph/ServerNotes.pdf

The latest howtos, which have been getting updated over the 
last few months, and are just about ready to go, contain an
updated discussion about [rw]mem_*, where I use the same examples,
but note that they apply to both read and write parameters.

As for limits, my paper notes much higher values than I was 
really willing to state in the howto.  Note that benchmarks are
often not real-world environments (I should probably remove the
"often" qualifier), so be sure to treat these suggestions with
a bit of skepticism.

I also corrected the fragmentation part to refer to all kernels.
The main thing to look for is MTU, plus the number of reassambly
failures noted as "reasmfails" in /proc/net/snmp, especially when
you start using 32K in udp (which is probably not the best idea).

Regards -

Tom


David Dougall wrote:
> 
> Looking through the nfs-howto chapter 5 "Optimizing NFS Performance", I
> found a few ambiguous statements and was wondering if I could get some
> clarification.
> There is a suggestion to increase rmem_default and rmem_max in
> /proc/sys/net/core to "at least 256k".  What is the limit on that?  If I
> have a server withs gobs of memory, how high can I increase that to still
> get performance improvements.  Are there some statistics I can use to
> measure if increases in this are helping.  Also, should I also increase
> wmem_default and wmem_max.  It makes no mention of that in the howto.
> 
> With respect to Overflow of fragmented packets, it mentions the 2.2
> kernel, but never mentions the 2.4.  Is it the same?  If so, it might be
> nice to clear that up in the howto.  It also states that there is no ideal
> value for this.  Any suggestions for specific traffic patterns?
> 
> Thanks
> --David Dougall
> 
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--
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Tom McNeal       trmcneal@attbi.com     (650)906-0761 (cell) 
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