Re: PREEMPT_RT vs I-PIPE: the numbers, part 2

From: Ingo Molnar
Date: Wed Jun 22 2005 - 15:23:15 EST

* Bill Huey <bhuey@xxxxxxxx> wrote:

> > target is subject to the HD test. For a pipe, this goes from 9.4us
> > to 21.6. For UDP this goes from 22us to 1070us !!! Even on a
> > system without any load, the numbers are similar. Ouch.
> I'm involved in other things now, but I wouldn't be surprised if it
> was some kind of scheduler bug + softirq wacked interaction. [...]

the UDP-over-localhost latency was a softirq processing bug that is
fixed in current PREEMPT_RT patches. (real over-the-network latency was
never impacted, that's why it wasnt noticed before.)

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