Lines Matching +full:ideal +full:- +full:factor +full:- +full:value
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
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
248 The maximum limit for ``@max_active`` is 512 and the default value used
250 such that they are not the limiting factor while providing protection in
384 worker on the same CPU. This makes unbound workqueues behave as per-cpu
419 item starts execution, workqueue makes a best-effort attempt to ensure
436 It'd be ideal if an unbound workqueue's behavior is optimal for vast
438 kernel, there exists a pronounced trade-off between locality and utilization
445 testing with dm-crypt clearly illustrates this trade-off.
447 The tests are run on a CPU with 12-cores/24-threads split across four L3
449 ``/dev/dm-0`` is a dm-crypt device created on NVME SSD (Samsung 990 PRO) and
454 -------------------------------------------------------------
458 $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k --ioengine=libaio \
459 --iodepth=64 --runtime=60 --numjobs=24 --time_based --group_reporting \
460 --name=iops-test-job --verify=sha512
462 There are 24 issuers, each issuing 64 IOs concurrently. ``--verify=sha512``
469 .. list-table::
471 :header-rows: 1
473 * - Affinity
474 - Bandwidth (MiBps)
475 - CPU util (%)
477 * - system
478 - 1159.40 ±1.34
479 - 99.31 ±0.02
481 * - cache
482 - 1166.40 ±0.89
483 - 99.34 ±0.01
485 * - cache (strict)
486 - 1166.00 ±0.71
487 - 99.35 ±0.01
491 machine but the cache-affine ones outperform by 0.6% thanks to improved
496 -----------------------------------------------------
500 $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k \
501 --ioengine=libaio --iodepth=64 --runtime=60 --numjobs=8 \
502 --time_based --group_reporting --name=iops-test-job --verify=sha512
504 The only difference from the previous scenario is ``--numjobs=8``. There are
508 .. list-table::
510 :header-rows: 1
512 * - Affinity
513 - Bandwidth (MiBps)
514 - CPU util (%)
516 * - system
517 - 1155.40 ±0.89
518 - 97.41 ±0.05
520 * - cache
521 - 1154.40 ±1.14
522 - 96.15 ±0.09
524 * - cache (strict)
525 - 1112.00 ±4.64
526 - 93.26 ±0.35
539 -----------------------------------------------------------
543 $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k \
544 --ioengine=libaio --iodepth=64 --runtime=60 --numjobs=4 \
545 --time_based --group_reporting --name=iops-test-job --verify=sha512
547 Again, the only difference is ``--numjobs=4``. With the number of issuers
551 .. list-table::
553 :header-rows: 1
555 * - Affinity
556 - Bandwidth (MiBps)
557 - CPU util (%)
559 * - system
560 - 993.60 ±1.82
561 - 75.49 ±0.06
563 * - cache
564 - 973.40 ±1.52
565 - 74.90 ±0.07
567 * - cache (strict)
568 - 828.20 ±4.49
569 - 66.84 ±0.29
576 ------------------------------
583 While the loss of work-conservation in certain scenarios hurts, it is a lot
594 ``WQ_CPU_INTENSIVE`` per-cpu workqueue. There is no real advanage to the
600 * The loss of work-conservation in non-strict affinity scopes is likely
603 work-conservation in most cases. As such, it is possible that future
645 pod_node [0]=-1
651 pool[01] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 0
653 pool[03] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 1
655 pool[05] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 2
657 pool[07] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 3
661 pool[11] ref= 1 nice=-20 idle/workers= 1/ 1 cpus=0000000f
662 pool[12] ref= 2 nice=-20 idle/workers= 1/ 1 cpus=00000003
663 pool[13] ref= 2 nice=-20 idle/workers= 1/ 1 cpus=0000000c
665 Workqueue CPU -> pool
691 events 18545 0 6.1 0 5 - -
692 events_highpri 8 0 0.0 0 0 - -
693 events_long 3 0 0.0 0 0 - -
694 events_unbound 38306 0 0.1 - 7 - -
695 events_freezable 0 0 0.0 0 0 - -
696 events_power_efficient 29598 0 0.2 0 0 - -
697 events_freezable_pwr_ef 10 0 0.0 0 0 - -
698 sock_diag_events 0 0 0.0 0 0 - -
701 events 18548 0 6.1 0 5 - -
702 events_highpri 8 0 0.0 0 0 - -
703 events_long 3 0 0.0 0 0 - -
704 events_unbound 38322 0 0.1 - 7 - -
705 events_freezable 0 0 0.0 0 0 - -
706 events_power_efficient 29603 0 0.2 0 0 - -
707 events_freezable_pwr_ef 10 0 0.0 0 0 - -
708 sock_diag_events 0 0 0.0 0 0 - -
755 Non-reentrance Conditions
758 Workqueue guarantees that a work item cannot be re-entrant if the following
766 executed by at most one worker system-wide at any given time.
776 .. kernel-doc:: include/linux/workqueue.h
778 .. kernel-doc:: kernel/workqueue.c