Re: Real-Time Preemption, comparison to 2.6.10-mm1

[Mark_H_Johnson]

K.R. Foley wrote:
>Mark_H_Johnson@xxxxxxxxxxxx wrote:
[snip - long explanation of how a nice application can starve a non
nice application for minutes at a time on an SMP system]

>> My point was that -mm definitely has the problem (though to a lesser
>> degree). The tests I ran showed it on both the disk read and disk copy
>> stress tests. I guess I should try a vanilla 2.6.10 run as well to see
>> if it is something introduced in the -mm series (it certainly is not a
>> recent change...).
>
>I'm curious if anyone is seeing this behavior on UP systems, or is it
>only happening on SMP?
The build of 2.6.10 vanilla just completed and I reran my tests with
SMP and with MAXCPUS=1 (UP w/ SMP kernel).

The vanilla 2.6.10 kernel has the non RT starvation problem as well
for both test runs. It looks like this is not something in -mm but a
change between 2.4 and 2.6.

I did notice the test results were a little inconsistent between the
two runs...
             2.6.10 SMP    2.6.10 UP (w/ SMP kernel)
disk write    starved          OK
disk copy        OK         starved
disk read     starved       starved
but in both cases, a non nice (non RT) disk application was
starved by a nice (non RT) cpu application for minutes.

I wonder who I should be talking to next (or submit a bug report?)
about this.

  --Mark

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