Lines Matching +full:current +full:- +full:regulated
33 thread system-wide. A single MT wq needed to keep around the same
60 * Use per-CPU unified worker pools shared by all wq to provide
85 worker-pools.
87 The cmwq design differentiates between the user-facing workqueues that
89 which manages worker-pools and processes the queued work items.
91 There are two worker-pools, one for normal work items and the other
93 worker-pools to serve work items queued on unbound workqueues - the
98 Each per-CPU BH worker pool contains only one pseudo worker which represents
110 When a work item is queued to a workqueue, the target worker-pool is
112 and appended on the shared worklist of the worker-pool. For example,
114 be queued on the worklist of either normal or highpri worker-pool that
123 Each worker-pool bound to an actual CPU implements concurrency
124 management by hooking into the scheduler. The worker-pool is notified
130 workers on the CPU, the worker-pool doesn't start execution of a new
152 wq's that have a rescue-worker reserved for execution under memory
153 pressure. Else it is possible that the worker-pool deadlocks waiting
162 removal. ``alloc_workqueue()`` takes three arguments - ``@name``,
173 ---------
177 workqueues are always per-CPU and all BH work items are executed in the
188 worker-pools which host workers which are not bound to any
191 worker-pools try to start execution of work items as soon as
215 worker-pool of the target cpu. Highpri worker-pools are
218 Note that normal and highpri worker-pools don't interact with
226 worker-pool from starting execution. This is useful for bound
228 execution is regulated by the system scheduler.
232 regulated by the concurrency management and runnable
233 non-CPU-intensive work items can delay execution of CPU
240 --------------
245 at the same time per CPU. This is always a per-CPU attribute, even for
253 The number of active work items of a wq is usually regulated by the
389 worker on the same CPU. This makes unbound workqueues behave as per-cpu
417 Read to see the current affinity scope. Write to change.
419 When default is the current scope, reading this file will also show the
420 current effective scope in parentheses, for example, ``default (cache)``.
424 item starts execution, workqueue makes a best-effort attempt to ensure
442 majority of use cases without further tuning. Unfortunately, in the current
443 kernel, there exists a pronounced trade-off between locality and utilization
450 testing with dm-crypt clearly illustrates this trade-off.
452 The tests are run on a CPU with 12-cores/24-threads split across four L3
454 ``/dev/dm-0`` is a dm-crypt device created on NVME SSD (Samsung 990 PRO) and
459 -------------------------------------------------------------
463 $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k --ioengine=libaio \
464 --iodepth=64 --runtime=60 --numjobs=24 --time_based --group_reporting \
465 --name=iops-test-job --verify=sha512
467 There are 24 issuers, each issuing 64 IOs concurrently. ``--verify=sha512``
474 .. list-table::
476 :header-rows: 1
478 * - Affinity
479 - Bandwidth (MiBps)
480 - CPU util (%)
482 * - system
483 - 1159.40 ±1.34
484 - 99.31 ±0.02
486 * - cache
487 - 1166.40 ±0.89
488 - 99.34 ±0.01
490 * - cache (strict)
491 - 1166.00 ±0.71
492 - 99.35 ±0.01
496 machine but the cache-affine ones outperform by 0.6% thanks to improved
501 -----------------------------------------------------
505 $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k \
506 --ioengine=libaio --iodepth=64 --runtime=60 --numjobs=8 \
507 --time_based --group_reporting --name=iops-test-job --verify=sha512
509 The only difference from the previous scenario is ``--numjobs=8``. There are
513 .. list-table::
515 :header-rows: 1
517 * - Affinity
518 - Bandwidth (MiBps)
519 - CPU util (%)
521 * - system
522 - 1155.40 ±0.89
523 - 97.41 ±0.05
525 * - cache
526 - 1154.40 ±1.14
527 - 96.15 ±0.09
529 * - cache (strict)
530 - 1112.00 ±4.64
531 - 93.26 ±0.35
544 -----------------------------------------------------------
548 $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k \
549 --ioengine=libaio --iodepth=64 --runtime=60 --numjobs=4 \
550 --time_based --group_reporting --name=iops-test-job --verify=sha512
552 Again, the only difference is ``--numjobs=4``. With the number of issuers
556 .. list-table::
558 :header-rows: 1
560 * - Affinity
561 - Bandwidth (MiBps)
562 - CPU util (%)
564 * - system
565 - 993.60 ±1.82
566 - 75.49 ±0.06
568 * - cache
569 - 973.40 ±1.52
570 - 74.90 ±0.07
572 * - cache (strict)
573 - 828.20 ±4.49
574 - 66.84 ±0.29
581 ------------------------------
588 While the loss of work-conservation in certain scenarios hurts, it is a lot
599 ``WQ_CPU_INTENSIVE`` per-cpu workqueue. There is no real advanage to the
605 * The loss of work-conservation in non-strict affinity scopes is likely
608 work-conservation in most cases. As such, it is possible that future
650 pod_node [0]=-1
656 pool[01] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 0
658 pool[03] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 1
660 pool[05] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 2
662 pool[07] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 3
666 pool[11] ref= 1 nice=-20 idle/workers= 1/ 1 cpus=0000000f
667 pool[12] ref= 2 nice=-20 idle/workers= 1/ 1 cpus=00000003
668 pool[13] ref= 2 nice=-20 idle/workers= 1/ 1 cpus=0000000c
670 Workqueue CPU -> pool
696 events 18545 0 6.1 0 5 - -
697 events_highpri 8 0 0.0 0 0 - -
698 events_long 3 0 0.0 0 0 - -
699 events_unbound 38306 0 0.1 - 7 - -
700 events_freezable 0 0 0.0 0 0 - -
701 events_power_efficient 29598 0 0.2 0 0 - -
702 events_freezable_pwr_ef 10 0 0.0 0 0 - -
703 sock_diag_events 0 0 0.0 0 0 - -
706 events 18548 0 6.1 0 5 - -
707 events_highpri 8 0 0.0 0 0 - -
708 events_long 3 0 0.0 0 0 - -
709 events_unbound 38322 0 0.1 - 7 - -
710 events_freezable 0 0 0.0 0 0 - -
711 events_power_efficient 29603 0 0.2 0 0 - -
712 events_freezable_pwr_ef 10 0 0.0 0 0 - -
713 sock_diag_events 0 0 0.0 0 0 - -
760 Non-reentrance Conditions
763 Workqueue guarantees that a work item cannot be re-entrant if the following
771 executed by at most one worker system-wide at any given time.
781 .. kernel-doc:: include/linux/workqueue.h
783 .. kernel-doc:: kernel/workqueue.c