[PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Marco Crivellari]

Hi,

=== Current situation: problems ===

Let's consider a nohz_full system with isolated CPUs: wq_unbound_cpumask is
set to the housekeeping CPUs, for !WQ_UNBOUND the local CPU is selected.

This leads to different scenarios if a work item is scheduled on an
isolated CPU where "delay" value is 0 or greater then 0:
        schedule_delayed_work(, 0);

This will be handled by __queue_work() that will queue the work item on the
current local (isolated) CPU, while:

        schedule_delayed_work(, 1);

Will move the timer on an housekeeping CPU, and schedule the work there.

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 consistency cannot be addressed without refactoring the API.

=== Recent changes to the WQ API ===

The following, address the recent changes in the Workqueue API:

- commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
- commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")

The old workqueues will be removed in a future release cycle.

=== Introduced Changes by this series ===

1) [P 1]  Replace uses of system_unbound_wq

    system_unbound_wq is to be used when locality is not required.

    Because of that, system_unbound_wq has been replaced with
	system_dfl_wq, to make it clear it should be used if locality
	is not important.

2) [P 2] WQ_PERCPU added to alloc_workqueue()

    This change adds a new WQ_PERCPU flag to explicitly request
    alloc_workqueue() to be per-cpu when WQ_UNBOUND has not been specified.


Thanks!


Marco Crivellari (2):
  drm/nouveau: replace use of system_unbound_wq with system_dfl_wq
  drm/nouveau: WQ_PERCPU added to alloc_workqueue users

 drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +-
 drivers/gpu/drm/nouveau/nouveau_drm.c   | 2 +-
 drivers/gpu/drm/nouveau/nouveau_sched.c | 3 ++-
 3 files changed, 4 insertions(+), 3 deletions(-)

-- 
2.51.0

[PATCH 1/2] drm/nouveau: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

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 consistency cannot be addressed without refactoring the API.

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.

The old system_unbound_wq will be kept for a few release cycles.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index e97e39abf3a2..50b7aade5f0a 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -2474,7 +2474,7 @@ nv50_disp_atomic_commit(struct drm_device *dev,
 	pm_runtime_get_noresume(dev->dev);
 
 	if (nonblock)
-		queue_work(system_unbound_wq, &state->commit_work);
+		queue_work(system_dfl_wq, &state->commit_work);
 	else
 		nv50_disp_atomic_commit_tail(state);
 
-- 
2.51.0

Re: [PATCH 1/2] drm/nouveau: replace use of system_unbound_wq with system_dfl_wq

[Thomas Zimmermann]

Am 31.10.25 um 11:20 schrieb Marco Crivellari:
> 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 consistency cannot be addressed without refactoring the API.
>
> 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.
>
> The old system_unbound_wq will be kept for a few release cycles.
>
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>

> ---
>   drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> index e97e39abf3a2..50b7aade5f0a 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -2474,7 +2474,7 @@ nv50_disp_atomic_commit(struct drm_device *dev,
>   	pm_runtime_get_noresume(dev->dev);
>   
>   	if (nonblock)
> -		queue_work(system_unbound_wq, &state->commit_work);
> +		queue_work(system_dfl_wq, &state->commit_work);
>   	else
>   		nv50_disp_atomic_commit_tail(state);
>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)

[PATCH 2/2] drm/nouveau: WQ_PERCPU added to alloc_workqueue users

[Marco Crivellari]

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.

alloc_workqueue() treats all queues as per-CPU by default, while unbound
workqueues must opt-in via WQ_UNBOUND.

This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.

This change adds a new WQ_PERCPU flag to explicitly request
alloc_workqueue() to be per-cpu when WQ_UNBOUND has not been specified.

With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.

Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 drivers/gpu/drm/nouveau/nouveau_drm.c   | 2 +-
 drivers/gpu/drm/nouveau/nouveau_sched.c | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 1527b801f013..5a2970ef27d4 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -631,7 +631,7 @@ nouveau_drm_device_init(struct nouveau_drm *drm)
 	struct drm_device *dev = drm->dev;
 	int ret;
 
-	drm->sched_wq = alloc_workqueue("nouveau_sched_wq_shared", 0,
+	drm->sched_wq = alloc_workqueue("nouveau_sched_wq_shared", WQ_PERCPU,
 					WQ_MAX_ACTIVE);
 	if (!drm->sched_wq)
 		return -ENOMEM;
diff --git a/drivers/gpu/drm/nouveau/nouveau_sched.c b/drivers/gpu/drm/nouveau/nouveau_sched.c
index e60f7892f5ce..79cf157ab2a5 100644
--- a/drivers/gpu/drm/nouveau/nouveau_sched.c
+++ b/drivers/gpu/drm/nouveau/nouveau_sched.c
@@ -416,7 +416,8 @@ nouveau_sched_init(struct nouveau_sched *sched, struct nouveau_drm *drm,
 	int ret;
 
 	if (!wq) {
-		wq = alloc_workqueue("nouveau_sched_wq_%d", 0, WQ_MAX_ACTIVE,
+		wq = alloc_workqueue("nouveau_sched_wq_%d", WQ_PERCPU,
+				     WQ_MAX_ACTIVE,
 				     current->pid);
 		if (!wq)
 			return -ENOMEM;
-- 
2.51.0

Re: [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Marco Crivellari]

Hi,

On Fri, Oct 31, 2025 at 11:20 AM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> Marco Crivellari (2):
>   drm/nouveau: replace use of system_unbound_wq with system_dfl_wq
>   drm/nouveau: WQ_PERCPU added to alloc_workqueue users
>
>  drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +-
>  drivers/gpu/drm/nouveau/nouveau_drm.c   | 2 +-
>  drivers/gpu/drm/nouveau/nouveau_sched.c | 3 ++-
>  3 files changed, 4 insertions(+), 3 deletions(-)

Gentle ping.

Thanks!

-- 

Marco Crivellari

L3 Support Engineer, Technology & Product

Re: [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Marco Crivellari]

Hi,

On Tue, Dec 2, 2025 at 2:20 PM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> [...]
> > Marco Crivellari (2):
> >   drm/nouveau: replace use of system_unbound_wq with system_dfl_wq
> >   drm/nouveau: WQ_PERCPU added to alloc_workqueue users
> >
> >  drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +-
> >  drivers/gpu/drm/nouveau/nouveau_drm.c   | 2 +-
> >  drivers/gpu/drm/nouveau/nouveau_sched.c | 3 ++-
> >  3 files changed, 4 insertions(+), 3 deletions(-)
>
> Gentle ping.

Hi,

Gentle ping. :-)

Thanks!

-- 

Marco Crivellari

L3 Support Engineer

Re: [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Marco Crivellari]

Hi,

On Fri, Oct 31, 2025 at 11:20 AM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> Marco Crivellari (2):
>   drm/nouveau: replace use of system_unbound_wq with system_dfl_wq
>   drm/nouveau: WQ_PERCPU added to alloc_workqueue users
>
>  drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +-
>  drivers/gpu/drm/nouveau/nouveau_drm.c   | 2 +-
>  drivers/gpu/drm/nouveau/nouveau_sched.c | 3 ++-
>  3 files changed, 4 insertions(+), 3 deletions(-)

Gentle ping.

Thanks!

-- 

Marco Crivellari

L3 Support Engineer

Re: [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Marco Crivellari]

Hi,

On Fri, Oct 31, 2025 at 11:20 AM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> Marco Crivellari (2):
>   drm/nouveau: replace use of system_unbound_wq with system_dfl_wq
>   drm/nouveau: WQ_PERCPU added to alloc_workqueue users
>
>  drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +-
>  drivers/gpu/drm/nouveau/nouveau_drm.c   | 2 +-
>  drivers/gpu/drm/nouveau/nouveau_sched.c | 3 ++-
>  3 files changed, 4 insertions(+), 3 deletions(-)

Gentle ping.

Thanks!

-- 

Marco Crivellari

L3 Support Engineer

Re: [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Marco Crivellari]

On Fri, Oct 31, 2025 at 11:20 AM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> [...]
> Marco Crivellari (2):
>   drm/nouveau: replace use of system_unbound_wq with system_dfl_wq
>   drm/nouveau: WQ_PERCPU added to alloc_workqueue users
>
>  drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +-
>  drivers/gpu/drm/nouveau/nouveau_drm.c   | 2 +-
>  drivers/gpu/drm/nouveau/nouveau_sched.c | 3 ++-
>  3 files changed, 4 insertions(+), 3 deletions(-)

Hi,

Gentle ping.

Thanks!

-- 

Marco Crivellari

SUSE Labs

Re: [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Danilo Krummrich]

On Fri, 31 Oct 2025 11:20:18 +0100, Marco Crivellari wrote:
> [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

Applied, thanks!

  Branch: drm-misc-next
  Tree:   https://gitlab.freedesktop.org/drm/misc/kernel.git

[1/2] drm/nouveau: replace use of system_unbound_wq with system_dfl_wq
      commit: ef1b53284175
[2/2] drm/nouveau: WQ_PERCPU added to alloc_workqueue users
      commit: c82a16b0caac

The patches will appear in the next linux-next integration (typically within 24
hours on weekdays).

The patches are queued up for the upcoming merge window for the next major
kernel release.

Re: [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Marco Crivellari]

On Tue, Apr 28, 2026 at 12:59 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> On Fri, 31 Oct 2025 11:20:18 +0100, Marco Crivellari wrote:
> > [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue
>
> Applied, thanks!
>
>   Branch: drm-misc-next
>   Tree:   https://gitlab.freedesktop.org/drm/misc/kernel.git
>
> [1/2] drm/nouveau: replace use of system_unbound_wq with system_dfl_wq
>       commit: ef1b53284175
> [2/2] drm/nouveau: WQ_PERCPU added to alloc_workqueue users
>       commit: c82a16b0caac

Many thanks!

-- 

Marco Crivellari

SUSE Labs

Re: [PATCH 0/2] replaced old wq name, added WQ_PERCPU to alloc_workqueue

[Danilo Krummrich]

On 4/28/26 1:19 PM, Marco Crivellari wrote:
> Many thanks!
No worries, sorry for the delay.

- Danilo