IDS Forum

Re: Hyper threading

Posted By: Art Kagel
Date: Monday, 12 October 2015, at 8:53 p.m.

In Response To: Re: Hyper threading (JEFF POUTON)

Jeff:

Yes, I disagree with IBM based on testing I and several other DBAs did in
the mid '90s and my experiences since. I find that a CPU VP can't take
advantage of much more than about 500MHZ of processor cycles, so if you
want to get maximum throughput and responsiveness out of a systems for a
large number of active users, then configure two CPU VPs per GHZ.

Example: I was just looking at a client's machine. They have 8x2.4GHZ
processor cores and were running 8 CPU VPs. I ran top and the 8 CPU VPs
were running at the top of the process list constantly each using about 20%
of a CPU core and the machine was 88% idle. I added 8 more CPU VPs, idle
dropped only to between 80 & 84% but now the top 6 CPU VPs were only using
about 15% of a core with the bottom 6 using about 9%. More work was
getting done concurrently, users are experiencing a system that seems to be
more responsive and so faster, and nothing was lost.

Another client, a couple of months ago. They were running 5 cores with 20
CPU VPs (up from 5 before I got there) and were getting throughput from 150
sessions ranked at ~100 complex transactions/sec. They added another 5
cores but initially didn't add any CPU VPs, so 10 cores and 20 VPs.
Throughput rose a moderate 20% to 120 transactions/sec. I added another 20
CPU VPs so 20 cores and 40 VPs and throughput increased to over 200
transactions/sec. QED

Art

Art S. Kagel, President and Principal Consultant
ASK Database Management
www.askdbmgt.com

Blog: http://informix-myview.blogspot.com/

Disclaimer: Please keep in mind that my own opinions are my own opinions
and do not reflect on the IIUG, nor any other organization with which I am
associated either explicitly, implicitly, or by inference. Neither do
those opinions reflect those of other individuals affiliated with any
entity with which I am affiliated nor those of the entities themselves.

On Mon, Oct 12, 2015 at 8:28 PM, <> wrote:

> Art
>
> I'm interested in your comments
>
> "You need about 500MHZ of cpu cycles per CPU VP so for a 4GHZ processor you
> should be able to run 6-8 CPU VPs per core with positive performance gains
> from the 6th, 7th, & 8th VP. "
>
> My simple understanding, based on documentation is
>
> "On systems, where multi-core processors are installed, the optimal
> configuration in most cases is the same as for systems with a number of
> individual processors equal to the total number of cores. Setting the
> number
> of CPU VPs to N-1, where N is number of cores is close to optimal for
> CPU-intensive workloads."
>
> So if I understand your statement correctly we could have more CPU VP's
> than
> cores available. So if we're looking at a P8 with two 12-core 3.52 GHz
> POWER8
> processor cards we could in theory run 6 - 7 CPU VP's per core or 24 times
> this number. Of course we would not do this as the O/S needs some capacity.
>
> Thanks in advance.
>
> Jeff Poulton
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

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Messages In This Thread

• Hyper threading
  Peter.Logan@spartannash.com -- Monday, 12 October 2015, at 2:50 p.m.
  • Re: Hyper threading
    Paul Watson -- Monday, 12 October 2015, at 2:55 p.m.
  • Re: Hyper threading
    Art Kagel -- Monday, 12 October 2015, at 3:22 p.m.
    • Re: Hyper threading
      Paul Watson -- Monday, 12 October 2015, at 5:33 p.m.
    • Re: Hyper threading
      JEFF POUTON -- Monday, 12 October 2015, at 8:28 p.m.
      • Re: Hyper threading
        Art Kagel -- Monday, 12 October 2015, at 8:53 p.m.
        • Re: Hyper threading
          Fernando Nunes -- Tuesday, 13 October 2015, at 11:33 a.m.
      • Re: Hyper threading
        Art Kagel -- Monday, 12 October 2015, at 8:54 p.m.
      • Re: Hyper threading
        JEFF POUTON -- Monday, 12 October 2015, at 10:28 p.m.
        • Re: Hyper threading
          Art Kagel -- Monday, 12 October 2015, at 10:34 p.m.
    • Re: Hyper threading
      Peter.Logan@spartannash.com -- Tuesday, 13 October 2015, at 7:38 a.m.
      • Re: Hyper threading
        Paul Watson -- Tuesday, 13 October 2015, at 7:53 a.m.

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