Process & threads - Karmic vs past kernels

[Chase Douglas]

On Fri, Mar 12, 2010 at 10:17 AM, Peter Matulis
<peter.matulis at canonical.com> wrote:
> Chase Douglas wrote:
>> On Wed, Mar 10, 2010 at 3:45 PM, Peter Matulis
>> <peter.matulis at canonical.com> wrote:
>>> Can anyone tell me whether the Karmic kernel has implemented a different
>>> way of what it considers a process (as opposed to threads)?
>>>
>>> I have a situation where CPU load is zero on Karmic but considerably
>>> higher in Jaunty and earlier.
>>>
>>> The scenario is a single java process with many threads.  The system has
>>> 4 cores and only one java process should logically produce a negligible
>>> CPU load but why was this not the case with earlier kernels?  Has
>>> something changed in Karmic that would explain what I'm seeing?
>>
>> I doubt that to be the case. Have you been able to get more data for
>> your bug [1]?
>>
>> Thanks,
>> Chase
>>
>> [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/513848
>
> Yes, but I couldn't get as much CPU usage out of the Karmic test.  My
> 'top' results show the following:
>
> Cpu1  :  0.3%us,  0.6%sy
> Cpu2  :  2.4%us,  0.6%sy
> Cpu3  :  9.1%us,  1.8%sy
> Cpu4  : 16.0%us,  7.4%sy
>
> With a load of 0.00 across the board.
>
> Now since CPU1 has such a low usage it makes sense that load is
> negligible since that CPU is always available.  It seems that the
> question is now:
>
> Why the CPU usage is so much different between Karmic and Jaunty in this
>  (single process/multiple thread) scenario.

First, I really can't figure out why the load would be 0.00 in all the
screen shots you posted in the bug. If you really need to know why the
load is reporting as 0.00, I'd probably have to build a test kernel to
spit out some statistics each time it goes to calculate the load. Are
you interested enough to go down that route?

But, in your second question you seem to say that this isn't a huge
deal, but you wonder why the cpu usage is lower in Karmic than in
Jaunty. To which I also have no answer, but it sort of falls into the
"if it ain't broke, don't fix it" category for me.

-- Chase