Not to be pedantic, but my understanding and observation is that in a mixed workload environment, when push comes to shove because a CPU is busy supporting many active threads, the high-priority threads get attention while the low-priority threads get pushed down in the stack, and wait. In James' case, It could be that Tomcat is running at a lower priority and suffering from CPU starvation while high-priority jobs are not. Tomcat's CPU requirements are also relatively high compared to traditional workloads. If it is suffering from CPU starvation, it becomes more noticeable.

Granted, threads eventually get requested CPU, but they may have wait if push comes to shove.



----- Original Message -----
From: Jim Oberholtzer <midrangel@xxxxxxxxxxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
Cc:
Sent: Friday, April 13, 2012 1:21 PM
Subject: Re: Questions about subsystems and performance (both in general and specific to Tomcat)

Time slice and job priority do not affect the amount of CPU given to a
thread, only in what order the system pays attention to the thread, and
how long the thread can be in the active queue before another thread of
equal or higher priority kicks it out.  (with some of the system values
you can allow lower priority jobs to sneak in and get some attention)

Once the thread is active, it will get as much CPU as requested and
available.

Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects


On 4/13/2012 12:41 PM, Nathan Andelin wrote:
Good response, Jim. Perhaps one clarification is that you can assign job priority and time slice to sub-systems, which affect CPU allocations to servers like Tomcat.



----- Original Message -----
From: Jim Oberholtzer<midrangel@xxxxxxxxxxxxxxxxx>
To: Midrange Systems Technical Discussion<midrange-l@xxxxxxxxxxxx>
Cc:
Sent: Friday, April 13, 2012 10:46 AM
Subject: Re: Questions about subsystems and performance (both in general and specific to Tomcat)

In order:

Processor is not allocated at the subsystem level, rather at the
partition level.  While there are methods to control how much memory is
used by a subsystem and its jobs, there is no way I am aware of (at this
point) to control processor at the subsystem level.

Any subsystem will do, but you have to tune it properly.  I like to set
up routing to push specific workloads into shared memory pools where I
can not control some of the performance.

None of this is hard once you understand the job routing on the system.

Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects


On 4/13/2012 11:14 AM, James Lampert wrote:
  Questions from my boss:

  How does one tell which subsystem has more allocated processing power
  and memory?

  And when running Tomcat, is there a particular subsystem that it should
  be running in, for best performance?

  --
  JHHL
  --
--

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