Messages in this thread | | | Subject | Re: sched: fix/optimise some issues | From | Peter Zijlstra <> | Date | Thu, 21 Jul 2011 17:08:15 +0200 |
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On Wed, 2011-07-20 at 15:42 +0200, Stephan Bärwolf wrote: > > I also implemented an 128bit vruntime support: > Majorly on systems with many tasks and (for example) deep cgroups > (or increased NICE0_LOAD/ SCHED_LOAD_SCALE as in commit > c8b281161dfa4bb5d5be63fb036ce19347b88c63), a weighted timeslice > (unsigned long) can become very large (on x86_64) and consumes a > large part of the u64 vruntimes (per tick) when added. > This might lead to missscheduling because of overflows.
Right, so I've often wanted a [us]128 type, and gcc has some (broken?) support for that, but overhead has always kept me from it.
There's also the non-atomicy thing to consider, see min_vruntime_copy etc.
How horrid is the current vruntime situation?
As to your true-idle, there's a very good reason the current SCHED_IDLE isnt' a true idle scheduler; it would create horrid priority inversion problems, imagine the true idle task holding a mutex or is required to complete something.
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