Messages in this thread | | | Subject | Re: [PATCH] new irq tracer | From | Peter Zijlstra <> | Date | Fri, 27 Feb 2009 08:23:14 +0100 |
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On Fri, 2009-02-27 at 12:14 +0900, KOSAKI Motohiro wrote: > > > > Given this scenario : > > > > > > > > A telecommunication system runs, but the client notices > > > something wrong. > > > > They call their service provider. The provider enables tracing > > > > _remotely_ on the _production system_ while it's _active in > > > the field_. > > > > > > > > Bam, those few milliseconds interrupt latencies become unacceptable. > > > > > > > > Hopefully this scenario makes the use-case clearer. The > > > problem is not > > > > that interrupt latencies would occur while tracing is on, > > > but rather > > > > that it would happen on a running production system when switching > > > > tracing on. This is what is totally unacceptable for this use-case. > > > > > > > > For more details about such requirements, I'm CCing > > > Dominique Toupin > > > > from Ericsson who I'm sure would be happy to give more > > > details about > > > > this if needed. > > > > > > Hmm, so this system in the field is running Linux with the > > > Real-Time Patch? Because if it isn't it will suffer from > > > millisecond latencies in normal operation. > > > > In many cases we don't use Linux real-time, we have many systems that > > are soft-real-time an non real-time Linux is good enough. > > > > Agreed, rt-patch seems off topics. we discuss to mainline kernel.
Exactly, hence you should not worry about ms irq-off latencies, since mainline is happy to generate those for you, regardless of function-trace.
The only way to complain about those is if your base system is better than that, and currently only preempt-rt provides that.
So unless you're on preempt-rt, complaining about ms-order irq latencies just isn't a valid argument.
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