Lines Matching refs:CPU
5 1. CPU Capacity
16 CPU capacity is a measure of the performance a CPU can reach, normalized against
17 the most performant CPU in the system. Heterogeneous systems are also called
18 asymmetric CPU capacity systems, as they contain CPUs of different capacities.
20 Disparity in maximum attainable performance (IOW in maximum CPU capacity) stems
32 CPU performance is usually expressed in Millions of Instructions Per Second
41 Two different capacity values are used within the scheduler. A CPU's
43 attainable performance level. A CPU's ``capacity`` is its ``capacity_orig`` to
47 Note that a CPU's ``capacity`` is solely intended to be used by the CFS class,
58 Consider an hypothetical dual-core asymmetric CPU capacity system where
103 Executing the same workload as described in 1.3.1, which each CPU running at its
120 It should be noted that having a *single* value to represent differences in CPU
133 regards to CPU capacity. Each scheduler class can express this differently, and
144 spends more time sleeping than executing. Variable CPU frequencies and
145 asymmetric CPU capacities complexify this somewhat; the following sections will
152 directly impacted by the current OPP the CPU is running at. Consider running a
155 CPU work ^
164 CPU work ^
180 2.3 CPU invariance
183 CPU capacity has a similar effect on task utilization in that running an
192 Executing a given periodic workload on each CPU at their maximum frequency would
210 The task utilization signal can be made CPU invariant using the following
215 with ``max_capacity`` being the highest CPU capacity value in the
216 system. Applying this formula to the above example above yields a CPU
222 Both frequency and CPU invariance need to be applied to task utilization in
224 utilization that is both CPU and frequency invariant is thus, for a given
232 if it were running on the highest-capacity CPU in the system, running at its
243 maintains a handful of CPU and task signals based on the Per-Entity Load
254 3.1 CPU capacity
257 Linux cannot currently figure out CPU capacity on its own, this information thus
262 CPU scaling data, which is derived from the capacity-dmips-mhz CPU binding; see
272 Implementing this function requires figuring out at which frequency each CPU
274 whose increment rate scale with a CPU's current frequency (APERF/MPERF on x86,
283 whether the system exhibits asymmetric CPU capacities. Should that be the
288 spans all unique CPU capacity values.
291 cater to asymmetric CPU capacity systems. Do note however that said key is
315 Since there *is* CPU capacity asymmetry in the system, the
321 asymmetric CPU capacities is to:
326 CPU or group thereof)
342 task "fits" on its CPU. If it is violated, the task will need to achieve more
343 work than what its CPU can provide: it will be CPU-bound.
350 5.1.2 Wakeup CPU selection
353 CFS task wakeup CPU selection follows the capacity fitness criterion described
355 which lets userspace have more leverage over the CPU selection of CFS
356 tasks. IOW, CFS wakeup CPU selection searches for a CPU that satisfies::
361 on any CPU by giving it a low uclamp.max value. Conversely, it can force a small
367 Wakeup CPU selection in CFS can be eclipsed by Energy Aware Scheduling
373 A pathological case in the wakeup CPU selection occurs when a task rarely
382 CPU work ^
389 CPU work ^
402 then it might become CPU-bound, IOW ``task_util(p) > capacity(task_cpu(p))``;
403 the CPU capacity scheduling criterion is violated, and there may not be any more
404 wakeup event to fix this up via wakeup CPU selection.
411 to a CPU with more capacity than its current one.
416 5.2.1 Wakeup CPU selection
419 RT task wakeup CPU selection searches for a CPU that satisfies::
425 is followed and CPU capacities are ignored.
430 5.3.1 Wakeup CPU selection
433 DL task wakeup CPU selection searches for a CPU that satisfies::
439 task will remain on its current CPU.