On 2012-05-09, Grant Edwards <grant.b.edwards@xxxxxxxxx> wrote:
> IOW: the real-time patch for 2.6.33.7 makes both the typical interrupt
> latency and the CPU usage significantly worse.
>
> Typical latency without the RT patch is 5-15us.
>
> Typical latency with is 15-50us (I've never seen latency below 15us
> with the RT patch).
>
> Is this the expected behavior?
I've been loaned a clue by somebody on the OSADL mailing list: the RT
patches are for improving _user_space_ reponse, and may do so at the
expense of both CPU usage and interrupt latency.
As a result, I'm better off without the RT patch if what I care about
is interrupt latency.
Am right I correct in the following conclusions?
* In 2.6.33.7, ISRs are really ISRs
* In 2.6.33.7-rt30, ISRs are kernel threads.
--
Grant Edwards grant.b.edwards Yow! Don't hit me!! I'm in
at the Twilight Zone!!!
gmail.com
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