Commit 128ea9f6 authored by Marco Crivellari's avatar Marco Crivellari Committed by Tejun Heo
Browse files

workqueue: Add system_percpu_wq and system_dfl_wq 



Currently, if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users. Make it
clear by adding a system_percpu_wq.

system_unbound_wq should be the default workqueue so as not to enforce
locality constraints for random work whenever it's not required.

Adding system_dfl_wq to encourage its use when unbound work should be used.

Suggested-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarMarco Crivellari <marco.crivellari@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 0ff41df1

include/linux/workqueue.h

+5 −3
Original line number Diff line number Diff line
@@ -427,7 +427,7 @@ enum wq_consts { 
/*

 * System-wide workqueues which are always present.

 *

 * system_wq is the one used by schedule[_delayed]_work[_on]().

 * system_percpu_wq is the one used by schedule[_delayed]_work[_on]().

 * Multi-CPU multi-threaded.  There are users which expect relatively

 * short queue flush time.  Don't queue works which can run for too

 * long.
@@ -438,7 +438,7 @@ enum wq_consts { 
 * system_long_wq is similar to system_wq but may host long running

 * works.  Queue flushing might take relatively long.

 *

 * system_unbound_wq is unbound workqueue.  Workers are not bound to

 * system_dfl_wq is unbound workqueue.  Workers are not bound to

 * any specific CPU, not concurrency managed, and all queued works are

 * executed immediately as long as max_active limit is not reached and

 * resources are available.
@@ -455,10 +455,12 @@ enum wq_consts { 
 * system_bh[_highpri]_wq are convenience interface to softirq. BH work items

 * are executed in the queueing CPU's BH context in the queueing order.

 */

extern struct workqueue_struct *system_wq;

extern struct workqueue_struct *system_wq; /* use system_percpu_wq, this will be removed */

extern struct workqueue_struct *system_percpu_wq;

extern struct workqueue_struct *system_highpri_wq;

extern struct workqueue_struct *system_long_wq;

extern struct workqueue_struct *system_unbound_wq;

extern struct workqueue_struct *system_dfl_wq;

extern struct workqueue_struct *system_freezable_wq;

extern struct workqueue_struct *system_power_efficient_wq;

extern struct workqueue_struct *system_freezable_power_efficient_wq;

kernel/workqueue.c

+9 −4
Original line number Diff line number Diff line
@@ -505,12 +505,16 @@ static struct kthread_worker *pwq_release_worker __ro_after_init; 


struct workqueue_struct *system_wq __ro_after_init;

EXPORT_SYMBOL(system_wq);

struct workqueue_struct *system_percpu_wq __ro_after_init;

EXPORT_SYMBOL(system_percpu_wq);

struct workqueue_struct *system_highpri_wq __ro_after_init;

EXPORT_SYMBOL_GPL(system_highpri_wq);

struct workqueue_struct *system_long_wq __ro_after_init;

EXPORT_SYMBOL_GPL(system_long_wq);

struct workqueue_struct *system_unbound_wq __ro_after_init;

EXPORT_SYMBOL_GPL(system_unbound_wq);

struct workqueue_struct *system_dfl_wq __ro_after_init;

EXPORT_SYMBOL_GPL(system_dfl_wq);

struct workqueue_struct *system_freezable_wq __ro_after_init;

EXPORT_SYMBOL_GPL(system_freezable_wq);

struct workqueue_struct *system_power_efficient_wq __ro_after_init;
@@ -7816,10 +7820,11 @@ void __init workqueue_init_early(void) 
	}



	system_wq = alloc_workqueue("events", 0, 0);

	system_percpu_wq = alloc_workqueue("events", 0, 0);

	system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);

	system_long_wq = alloc_workqueue("events_long", 0, 0);

	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,

					    WQ_MAX_ACTIVE);

	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_MAX_ACTIVE);

	system_dfl_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_MAX_ACTIVE);

	system_freezable_wq = alloc_workqueue("events_freezable",

					      WQ_FREEZABLE, 0);

	system_power_efficient_wq = alloc_workqueue("events_power_efficient",
@@ -7830,8 +7835,8 @@ void __init workqueue_init_early(void) 
	system_bh_wq = alloc_workqueue("events_bh", WQ_BH, 0);

	system_bh_highpri_wq = alloc_workqueue("events_bh_highpri",

					       WQ_BH | WQ_HIGHPRI, 0);

	BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||

	       !system_unbound_wq || !system_freezable_wq ||

	BUG_ON(!system_wq || !system_percpu_wq|| !system_highpri_wq || !system_long_wq ||

	       !system_unbound_wq || !system_freezable_wq || !system_dfl_wq ||

	       !system_power_efficient_wq ||

	       !system_freezable_power_efficient_wq ||

	       !system_bh_wq || !system_bh_highpri_wq);