Mailinglist Archive: opensuse (2161 mails)

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Re: [opensuse] how to figure out, where is the bottleneck
  • From: "Sebastian Reitenbach" <sebastia@xxxxxxxxxxxxxxxxxxxx>
  • Date: Wed, 13 Aug 2008 14:22:18 +0200
  • Message-id: <20080813122218.E5143D26BA@xxxxxxxxxxxxxxxxxxxxxxxxx>
Hi,

thank you for your answer, comments inline:
"John Andersen" <jsamyth@xxxxxxxxx> wrote:
On Tue, Aug 12, 2008 at 9:36 AM, Sebastian Reitenbach
<sebastia@xxxxxxxxxxxxxxxxxxxx> wrote:
Hi,

I've three subsystems of a complex software architecture running on one
host
with 16CPU's, when the system runs under load, top shows me that the load
goes up to 40 and more, but I think a good value should be sth. between
16
and 20, and I have the fear, that the box at some point becomes more busy
with context switching than with the jobs I give to it.
top shows me that at least, the box is not swapping.
The output of iostat tells me, that the problem is not waiting for IO, so
the values there, are not unusually high.

Maybe I've just too many processes running at the same time?
But before I want to touch the system, and make changes, I'd really make
sure I found the bottleneck, at least with the tools mentioned above,
I've
no real clue yet.
Any recommendation to other tools, I could run, or files to check, to
monitor the system when it is under high load?

kind regards
Sebastian


But is it fast?

You mention only the numbers, not the thru-put. Is it doing the job?You
Its doing its job, but I've the feeling, that it could be a lot faster, but
maybe I'm wrong here. Therefore I was looking how to prove or dismiss my
assumption.


On a busy machine doing lots of work its not unreasonable for there to be
two or three tasks waiting per thread. If you have lots of processors
chances
are it just gets busier.

You can set affinity of each of these tasks giving them one or two
processors
to run on, but usually the system does a better job of that than you could.

Then I keep my finger away from that.

I found that I can change the I/O scheduling algorithm, as explained here:
http://www.redhat.com/magazine/008jun05/features/schedulers/
, and then rerun the tests, but as far as I can see, I don't think I have an
I/O problem.
But as far as I can see, I cannot do the same to choose a different process
scheduler?


Are these three tasks waiting for each other?
these three tasks are independent of each other, none waits on output of the
others.

kind regards
Sebastian

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