Lines Matching +full:no +full:- +full:idle
24 there is no work item left on the workqueue the worker becomes idle.
33 thread system-wide. A single MT wq needed to keep around the same
50 limitation that no two polling PIOs can progress at the same time. As
60 * Use per-CPU unified worker pools shared by all wq to provide
83 the functions off of the queue, one after the other. If no work is queued,
84 the worker threads become idle. These worker threads are managed in
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
97 concurrent execution context, there's no need to worry about concurrency.
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
132 schedules a new worker so that the CPU doesn't sit idle while there
136 Keeping idle workers around doesn't cost other than the memory space
137 for kthreads, so cmwq holds onto idle ones for a while before killing
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``,
166 A wq no longer manages execution resources but serves as a domain for
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
205 suspend operations. Work items on the wq are drained and no
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
262 ``WQ_UNBOUND`` used to achieve this behavior, this is no longer the
346 * Unless strict ordering is required, there is no need to use ST wq.
356 special attribute, can use one of the system wq. There is no
384 worker on the same CPU. This makes unbound workqueues behave as per-cpu
400 All CPUs are put in the same group. Workqueue makes no effort to process a
419 item starts execution, workqueue makes a best-effort attempt to ensure
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
489 With enough issuers spread across the system, there is no downside to
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
588 * As there is no one option which is great for most cases, workqueue usages
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
601 originating from the scheduler. There is no theoretical reason why the
603 work-conservation in most cases. As such, it is possible that future
645 pod_node [0]=-1
650 pool[00] ref= 1 nice= 0 idle/workers= 4/ 4 cpu= 0
651 pool[01] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 0
652 pool[02] ref= 1 nice= 0 idle/workers= 4/ 4 cpu= 1
653 pool[03] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 1
654 pool[04] ref= 1 nice= 0 idle/workers= 4/ 4 cpu= 2
655 pool[05] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 2
656 pool[06] ref= 1 nice= 0 idle/workers= 3/ 3 cpu= 3
657 pool[07] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 3
658 pool[08] ref=42 nice= 0 idle/workers= 6/ 6 cpus=0000000f
659 pool[09] ref=28 nice= 0 idle/workers= 3/ 3 cpus=00000003
660 pool[10] ref=28 nice= 0 idle/workers= 17/ 17 cpus=0000000c
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
762 2. No one queues the work item to another workqueue.
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