Documentation/scheduler/sched-bwc.rst

7    The SCHED_RT case is covered in Documentation/scheduler/sched-rt-group.rst
14 microseconds of CPU time. That quota is assigned to per-cpu run queues in
17 throttled. Throttled threads will not be able to run again until the next
22 is transferred to cpu-local "silos" on a demand basis. The amount transferred
26 -------------
27 This feature borrows time now against our future underrun, at the cost of
30 Traditional (UP-EDF) bandwidth control is something like:
36 we'd have to run more than a second of program time, and obviously miss
38 never time to catch up, unbounded fail.
52 everything is good. At the same time we have a p(5)p(5) = 0.25% chance
53 both tasks will exceed their quota at the same time (guaranteed deadline
58 At the same time, we can say that the worst case deadline miss, will be
66 https://lore.kernel.org/lkml/5371BD36-55AE-4F71-B9D7-B86DC32E3D2B@linux.alibaba.com/
69 ----------
75    :ref:`Documentation/admin-guide/cgroup-v2.rst <cgroup-v2-cpu>`.
77 - cpu.cfs_quota_us: run-time replenished within a period (in microseconds)
78 - cpu.cfs_period_us: the length of a period (in microseconds)
79 - cpu.stat: exports throttling statistics [explained further below]
80 - cpu.cfs_burst_us: the maximum accumulated run-time (in microseconds)
85 	cpu.cfs_quota_us=-1
88 A value of -1 for cpu.cfs_quota_us indicates that the group does not have any
90 bandwidth group. This represents the traditional work-conserving behavior for
112 --------------------
113 For efficiency run-time is transferred between the global pool and CPU local
115 on large systems. The amount transferred each time such an update is required
123 for more fine-grained consumption.
126 ----------
131 - nr_periods: Number of enforcement intervals that have elapsed.
132 - nr_throttled: Number of times the group has been throttled/limited.
133 - throttled_time: The total time duration (in nanoseconds) for which entities
135 - nr_bursts: Number of periods burst occurs.
136 - burst_time: Cumulative wall-time (in nanoseconds) that any CPUs has used
139 This interface is read-only.
142 ---------------------------
144 attainable, that is: max(c_i) <= C. However, over-subscription in the
145 aggregate case is explicitly allowed to enable work-conserving semantics
162 ---------------------------
165 unrunnable. This is configured at compile time by the min_cfs_rq_runtime
169 The fact that cpu-local slices do not expire results in some interesting corner
174 quota as well as the entirety of each cpu-local slice in each period. As a
178 For highly-threaded, non-cpu bound applications this non-expiration nuance
185 average usage, albeit over a longer time window than a single period.  This
192 possibility of wastefully expiring quota on cpu-local silos that don't need a
193 full slice's amount of cpu time.
195 The interaction between cpu-bound and non-cpu-bound-interactive applications
197 gave each of these applications half of a cpu-core and they both got scheduled
198 on the same CPU it is theoretically possible that the non-cpu bound application
200 cpu-bound application from fully using its quota by that same amount. In these
201 instances it will be up to the CFS algorithm (see sched-design-CFS.rst) to
202 decide which application is chosen to run, as they will both be runnable and
207 --------
216 2. Limit a group to 2 CPUs worth of runtime on a multi-CPU machine