Re: [PATCH] Avoid moving tasks when a schedule can be made.

[Nick Piggin <nickpiggin@yahoo.com.au>]

Ingo Molnar wrote:
> * Nick Piggin <nickpiggin@yahoo.com.au> wrote:

>>Oh, I forgot: Ingo once introduced some code to bail early (though for 
>>different reasons and under different conditions), and this actually 
>>was found to cause significant regressions in some database workloads.
> 
> 
> well, we both did changes with that effect - pretty much any change in 
> this area can cause a regression on _some_ workload ;) So there wont be 
> any silver bullet.
> 

Well yes. Although specifically the bail-out-early stuff which IIRC
you did... I wasn't singling you out in particular, I've broken the
scheduler at _least_ as much as you have since starting work on it ;)

> 
>>So it is not a nice thing to tinker with unless there is good reason.
> 
> 
> unbound latencies with hardirqs off are obviously a good reason - but i 
> agree that the solution is not good enough, yet.
> 

Ah, so this is an RT tree thing where the scheduler lock turns off "hard
irqs"? As opposed to something like the rwsem lock that only turns off
your "soft irqs" (sorry, I'm not with the terminlogy)?

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SUSE Labs, Novell Inc.
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