| Commit message (Collapse) | Author | Age |
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This patch introduces an Earliest-Deadline Zero-Laxity scheduler.
Jobs are normally scheduled by globally by deadline. However, jobs
with zero-laxity are given priority over jobs with laxity (aka slack).
Each job on the ready queue uses a timer to track points of
zero-laxity. Scheduled jobs have no need of timers.
Ties are broken by EDF if there exist more jobs with zero-laxity
than processors.
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To date, Litmus has just hooked into the smp_send_reschedule() IPI
handler and marked tasks as having to reschedule to implement remote
preemptions. This was never particularly clean, but so far we got away
with it. However, changes in the underlying Linux, and peculartities
of the ARM code (interrupts enabled before context switch) break this
naive approach. This patch introduces new state-machine based remote
preemption support. By examining the local state before calling
set_tsk_need_resched(), we avoid confusing the underlying Linux
scheduler. Further, this patch avoids sending unncessary IPIs.
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Simple logic: if a task requires precise enforcement, then program a
hr-timer to fire when the task must be descheduled. When the timer
fires, simply activate the scheduler. When we switch to a different
task, either reprogram the timer or cancel it.
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The PFAIR plugin always implicitly assumed !NO_HZ (the schedule
is wrong if NO_HZ is enabled) and does not built if hrtimers are absent:
> litmus/built-in.o: In function `pfair_activate_plugin':
> sched_pfair.c:(.text+0x7f07): undefined reference to `cpu_stagger_offset'
> litmus/built-in.o: In function `init_pfair':
> sched_pfair.c:(.init.text+0x487): undefined reference to `cpu_stagger_offset'
cpu_stagger_offset() is only available if hrtimers are enabled.
This patch makes these dependencies explicit.
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C-EDF only makes sense on multicore platforms that have shared caches.
Make it possible to disable it on other platforms, in particular,
on those that do not export get_shared_cpu_map().
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Improved C-EDF plugin. C-EDF now supports different cluster sizes (based
on L2 and L3 cache sharing) and supports dynamic changes of cluster size
(this requires reloading the plugin).
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This device only supports mmap()'ing a single page.
This page is shared RW between the kernel and userspace.
It is inteded to allow near-zero-overhead communication
between the kernel and userspace. It's first use will be a
proper implementation of user-signaled
non-preemptable section support.
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- Binomial heap "heap" names conflicted with priority heap
of cgroup in kernel
- This patch change binomial heap "heap" names in "bheap"
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- insert arm_release_timer() in add_relese() path
- arm_release_timer() uses __hrtimer_start_range_ns() instead of
hrtimer_start() to avoid deadlock on rq->lock.
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infrastructure
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Still to be merged:
- arm_release_timer() with no rq locking
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Port 2008.3 Core LITMUS^RT infrastructure to Linux 2.6.32
litmus_sched_class implements 4 new methods:
- prio_changed:
void
- switched_to:
void
- get_rr_interval:
return infinity (i.e., 0)
- select_task_rq:
return current cpu
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