linux-kernel - Re: [PATCH 6/6] sched: disabled rt-bandwidth by default

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Date:	Tue, 19 Aug 2008 13:11:52 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel@...r.kernel.org,
	Stefani Seibold <stefani@...bold.net>,
	Dario Faggioli <raistlin@...ux.it>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 6/6] sched: disabled rt-bandwidth by default


* Ingo Molnar <mingo@...e.hu> wrote:

> The fixes look good to me, but this enabling of infinite RT task 
> lockups is not an improvement.
> 
> The thing is, i got far more bugreports about locked up RT tasks where 
> the lockup was unintentional, than real bugreports about anyone 
> _intending_ for the whole box to come to a grinding halt because a 
> high-prio RT tasks is monopolizing the CPU.
> 
> In fact there's only been this artificial test so far.
> 
> So could you please just increase the chunking to 10 seconds or so, 
> from the current 1 second? Anyone locking up the system for more than 
> 10 seconds via an RT task has to deal with many other issues already.
> 
> I.e. keep the system borderline debuggable (up to 10 seconds delays 
> are _not_ nice so people will notice) - but it's still a marked 
> improvement from completly locked up desktops.
> 
> And those who really need longer than 10 second periods can set it 
> higher, or even (if they want to live dangerously or run POSIX 
> conformance tests) make it infinite (set it to -1) - and will have to 
> deal with other things like the softlockup watchdog as well.
> 
> Ok?

ok - i've queued the fixes up in tip/sched/rt (not in tip/sched/urgent 
yet, they need a bit of test-time, but are potential v2.6.27 commits) - 
see the shortlog below.

	Ingo

------------------>
Ingo Molnar (1):
      sched: set rt-bandwidth period from 1 second to 10 seconds

Peter Zijlstra (5):
      sched: rt-bandwidth for user grouping interface
      sched: rt-bandwidth accounting fix
      sched: rt-bandwidth group disable fixes
      sched: extract walk_tg_tree()
      sched: rt-bandwidth fixes


 kernel/sched.c    |  215 +++++++++++++++++++++++++++++------------------------
 kernel/sched_rt.c |   16 ++--
 kernel/user.c     |    4 +-
 3 files changed, 129 insertions(+), 106 deletions(-)

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