From: Peter Zijlstra <peterz@infradead.org>
To: stephan.baerwolf@tu-ilmenau.de
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
ncrao@google.com
Subject: Re: sched: fix/optimise some issues
Date: Thu, 21 Jul 2011 17:08:15 +0200 [thread overview]
Message-ID: <1311260895.29152.153.camel@twins> (raw)
In-Reply-To: <4E26DB41.9070002@tu-ilmenau.de>
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.
next prev parent reply other threads:[~2011-07-21 15:08 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-20 13:42 sched: fix/optimise some issues Stephan Bärwolf
2011-07-20 19:11 ` Peter Zijlstra
2011-07-21 1:00 ` Mike Galbraith
2011-07-20 19:11 ` Peter Zijlstra
2011-07-20 19:11 ` Peter Zijlstra
2011-07-21 15:08 ` Peter Zijlstra [this message]
2011-07-21 16:36 ` Stephan Bärwolf
2011-07-21 16:32 ` Peter Zijlstra
2011-07-21 16:43 ` Peter Zijlstra
2011-07-21 16:51 ` Peter Zijlstra
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