RT-Preemption is causing Very-High Interrupt Latency

RT-Preemption is causing Very-High Interrupt Latency

[p_ashish]

I applied RT-preemption and High-Resolution Timer Patch to linux-2.6.19.2 . 
It gave satisfactory result for 'cyclic_test' and 
'HR-Timer clock-nanoSleep_test'. 

But the problem is that Interrupt Latency in much more than before. 
This is result which i got from my Interrupt Latency program.

WITH RT-preemption: 
(Max Latency= 513.1 micro seconds and Min Latency= 12.1 micro seconds)

WITHOUT RT-preemption:
(Max Latency= 13.1 micro seconds and Min Latency= 1.8 micro seconds)


Since, RT-preemption implements ISR like threads, so is this the reason for 
higher latency? Is there any way to improve this?

regards
~ashish






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Re: RT-Preemption is causing Very-High Interrupt Latency

[Peter Zijlstra]

On Sun, 2008-08-17 at 23:02 -0700, p_ashish wrote:
> I applied RT-preemption and High-Resolution Timer Patch to linux-2.6.19.2 

That is a very ancient kernel - please try .26-rt (or .24-rt which is
atm a little more stable).