Messages in this thread | | | Date | Tue, 30 Nov 2004 09:49:04 +0100 | From | Ingo Molnar <> | Subject | Re: Priority Inheritance Test (Real-Time Preemption) |
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* Esben Nielsen <simlo@phys.au.dk> wrote:
> > and i'm regularly testing this property with 'hackbench 50', which > > creates over a 1000 wildly scheduling non-RT tasks. Latency is not > > affected by such workloads. > > > > Probably not. Even while doing that you most likely wont build up wait > lists of more than 10, maybe 100 tasks? Doing full traversals with irq > disabled probably wont be meassureable!(?) compared to much other > stuff increasing responsible for the meassured latency.
there is no full list traversal of SCHED_NORMAL tasks, ever.
but the best way is to test this yourself, download Florian's rtc_wakeup from:
http://www.affenbande.org/~tapas/wiki/index.php?rtc_wakeup
and run it with the highest possible resolution, 8192 Hz:
chrt -f 98 -p `pidof 'IRQ 8'` chrt -f 99 -p `pidof 'IRQ 0'`
./rtc_wakeup -f 8192 -t 100000
in this mode rtc_wakeup will report the worst irq-delivery latency it measures. It will thus measure the combined effect of any type of scheduling or irqs-off latency to RT-tasks.
then download hackbench from:
http://developer.osdl.org/craiger/hackbench/
and try e.g.:
./hackbench 50
this will start 2x20x50 == 2000 SCHED_NORMAL threads, all performing a nice pattern of scheduling simulating a busy chat server workload with tons of messages going back and forth.
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