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Message-ID: <1311260895.29152.153.camel@twins> Date: Thu, 21 Jul 2011 17:08:15 +0200 From: Peter Zijlstra <peterz@...radead.org> To: stephan.baerwolf@...ilmenau.de Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>, ncrao@...gle.com Subject: Re: sched: fix/optimise some issues 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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