Also seeing 2 x quad-core system slower that 2 x dual core
Adam McDougall
mcdouga9 at egr.msu.edu
Fri Dec 7 13:38:15 PST 2007
On Fri, Dec 07, 2007 at 12:39:22PM +0000, Pete French wrote:
Just as a followup to this - I soent some time going through all
the suggestions and advice that people gave me regarding this problem.
It turns out that the newer servers shipped by HP have different cache
settings to the older ones on their RAID controllers, plus I get very
different results from my benchmarks depending on how long the machines
have been booted for and what activity has occurred on them (probably due to
things ending up in cache).
Upshot - if the machines are configured identically, and an identical install
is made and an identical test doen then we get identical performance as
expected.
Part of the reason for posting this though is that a lot of people have bbeen
worrying about 8x CPU performance, and this thread won't have helped. So
I wanted to say that now I am convinced that (for my workload) these machines
are fine. To the point where I have installed 7.0-BETA4 on the ten new
8 core servers for a very large load on th webfarm this morning. I'm pleased
toio say that it went off perfectly, the servers took the load and we had
no problems at all. We are running CGI scripts against mySQL under apache22
basically - which is a pretty common thing to do. Ia m using ULE and tthe
amd64 version of the OS.
7.0 is excellent as far as I am concerned, and I don't think people
should be worried about deploying it on 8 core machines. My experinec
has been that it is fine and is also somewhat faster than 6.3 on the same
hardware.
-pete.
I feel I have to throw in my experience too just for the archives. This
previous weekend I had the opportunity to play with a dual quad-core dell
precision 690, and I saw no huge performance problems. All around I was fairly
happy with standard compile tests, did some rm. I didn't do anything involved
like databases or php. I could do a buildkernel with a few additional kernel
modules in 29 seconds :) but buildworld doesn't seem to benefit much from -j16
on a 8 core (not unexpected). I didn't have any useful parallel loads to test
on it.
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