Messages in this thread | | | Subject | Re: [PATCH] [request for inclusion] Realtime LSM | From | utz lehmann <> | Date | Fri, 14 Jan 2005 04:26:35 +0100 |
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On Fri, 2005-01-14 at 13:42 +1100, Con Kolivas wrote: > utz lehmann wrote: > > On Fri, 2005-01-14 at 13:08 +1100, Con Kolivas wrote: > > > >>utz lehmann wrote: > >>>Just an idea. What about throttling runaway RT tasks? > >>>If the system spend more than 98% in RT tasks for 5s consider this as a > >>>_fatal error_. Print an error message and throttle RT tasks by inserting > >>>ticks where only SCHED_OTHER tasks allowed. For a limit of 98% this > >>>means one SCHED_OTHER only tick all 50 ticks. > >>> > >>>The limit and timeout should be configurable and of course it can be > >>>disabled. > >>> > >>>I know this is against RT task preempt all SCHED_OTHER but this is only > >>>for a fatal system state to be able to recover sanely. A locked up > >>>machine is is the worse alternative. > >> > >>There is a patch in -mm currently designed to use a sysrq key > >>combination which converts all real time tasks to sched normal to save > >>you if you desire in a lockup situation. We do want to preserve RT > >>scheduling behaviour at all times without caveats for privileged users. > > > > > > The sysrq is already in 2.6.10. I had to use it the last days a few > > times. But it does help if you have no access to the console. > > > > The RT throttling idea is not to change the behavior in normal > > conditions. It's only for a fatal system state. If you have a runaway RT > > task you can't guarantee the system is work properly anyway. It's > > blocking vital kernel threads, filesystems, swap, keyboard, ... > > I understand fully your concern. If such a thing were to be introduced > it would have to be disabled by default. Since I'm looking at > implementing such throttling for user RT tasks, it should be trivial to > add it to other RT tasks, and have 100% as the default cpu limit. How > does that sound?
Sounds good.-) The kernel should have 100% limit (disable) as default. Users and distros can change it to a sane value for there needs.
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