Messages in this thread | | | From | Mark_H_Johnson@raytheon ... | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm3-V0.7.23 | Date | Wed, 10 Nov 2004 08:08:11 -0600 |
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>> [4] Application level latencies are OK but not great. >> X test - only 90% of CPU loops are within 100 usec of nominal value. >> In previous RT kernels I got > 99% with 100 usec. > >this might be a side-effect of the chrt-ing of events/[0|1] and/or >ksoftirqd (which we did to debug the 'freeze' problems) - are those >still chrt-ed? For reference: # ps -eo pid,pri,rtprio,cmd | grep '\[' 1 23 - init [5] 2 139 99 [migration/0] 3 34 - [ksoftirqd/0] 4 34 - [desched/0] 5 139 99 [migration/1] 6 34 - [ksoftirqd/1] 7 34 - [desched/1] 8 41 1 [events/0] 9 41 1 [events/1] 10 34 - [khelper] 15 32 - [kthread] 27 34 - [kblockd/0] 28 34 - [kblockd/1] 36 24 - [khubd] 103 23 - [kswapd0] 104 32 - [aio/0] 105 33 - [aio/1] 180 139 99 [IRQ 8] 195 14 - [kseriod] 201 139 99 [IRQ 12] 237 139 99 [IRQ 14] 239 139 99 [IRQ 15] 278 139 99 [IRQ 1] 310 24 - [kirqd] 313 139 99 [IRQ 4] 320 24 - [kjournald] 605 139 99 [IRQ 10] 1206 24 - [kjournald] 1207 24 - [kjournald] 1309 139 99 [IRQ 3] 1323 31 - [IRQ 7] 1494 139 99 [IRQ 6] 1748 139 99 [IRQ 11] 14131 23 - [pdflush] 14242 24 - [pdflush] 17337 21 - grep \[
>Please review and double-check all SCHED_FIFO tasks in >the system and keep only those that are absolutely necessary for >latencytest's operation [i.e. the soundcard IRQ and latencytest itself] >- everything else should be SCHED_OTHER. Do latencies get any better if >you do this? I can, but that is not necessarily an "apples to apples" comparison. When I compare with 2.4 preempt + low latency kernels, the X stress test had > 99% of the samples within 100 usec of the nominal value. Don't forget - on a 2.4 kernel, the IRQ's are all unthreaded. On the 2.4 kernel, heavy disk I/O is where I get the worst behavior and even then, I get > 90% of samples within 100 usec.
I still maintain that a 2.6 RT kernel has to do as well or better than a 2.4 RT kernel (or else, why would I step up??).
--Mark
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