[CentOS] Hot swap CPU

Sat Jul 9 00:11:51 UTC 2005
Bryan J. Smith <b.j.smith at ieee.org>

On Fri, 2005-07-08 at 19:33 -0400, Peter Arremann wrote:
> Bruno, you can make benchmarks say whatever you want - and this one seems to 
> be one of the worst distortions I've seen in a while. 
> I know from personal experience that this isn't even close. dual xeon 
> 2.0Ghz/4GB is about the same performance as a quad 450Mhz E4500/4GB in 
> everything we're doing... 

For what?  That's the question.

> The TPC-C benchmarks (only official, impartial benchmarks I could find) are 
> even worse: 
> dual 3.6Ghz scored 63464
> 14 way 464Mhz E4500 scored 67103

But there are over a _dozen_ TPC-C benchmarks -- some scale linearly on
clusters, other prefer shared memory systems, some really taxi
interconnect and do much better on NUMA+"true systems" interconnects.

The more you go the latter, the more P4 MCH "sucks."  ;->

> Oracle has a word doc on their website talking about performance of a E4500 vs 
> a Dell box (http://download-west.oracle.com/owsf_2003/Oracleworld2003.doc) 
> where a quad xeon beats a quad E4500 by about 60% - and that was a quad 
> 700Mhz P3 based Xeon... 

Which has the ALU/FPU equivalent of a 1.1-1.5GHz P4.  Now the MCH of a
P4 is certainly better, but still not a NUMA/"true system" interconnect.
Which is why P3/P4 does _not_ scale well beyond 2 CPUs -- heck, the P4
really no better than P3, only some more throughput, but no less
contention (actually more in many cases).

Which is why I still recommend dual-P3 servers today, especially
refurbs, for the cost.

But here's the kicker ... "Simultaneously running 8 queries"

At that point, I'm _not_ taxing the interconnect at all.  So there's no
advantage to the NUMA/UPA architecture.

> Go search google for Xeon and E4500 and you'll see tons more of these 
> benchmarks - and they all tell the same story...

Of course, because they don't do a _full_ suite.

Compaq-Microsoft came out with a benchmark of the full TPC-C suite
awhile back showing how Windows clusters beat a Sun shared memory
system.  What they didn't focus on, unless you read the entire article,
is how the PC got _roasted_ -- by up to 10x -- on 4 of the 15 tests
because they really stressed the interconnect, and the contention of
memory access of threads.


-- 
Bryan J. Smith                                     b.j.smith at ieee.org 
--------------------------------------------------------------------- 
It is mathematically impossible for someone who makes more than you
to be anything but richer than you.  Any tax rate that penalizes them
will also penalize you similarly (to those below you, and then below
them).  Linear algebra, let alone differential calculus or even ele-
mentary concepts of limits, is mutually exclusive with US journalism.
So forget even attempting to explain how tax cuts work.  ;->