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drm/nouveau: WQ_PERCPU added to alloc_workqueue users

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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>
Link: https://patch.msgid.link/20251031102020.95349-3-marco.crivellari@suse.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Marco Crivellari 2025-10-31 11:20:20 +01:00 committed by Danilo Krummrich
parent ef1b532841
commit c82a16b0ca
2 changed files with 3 additions and 2 deletions
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2
drivers/gpu/drm/nouveau/nouveau_drm.c
View File

@ -632,7 +632,7 @@ 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;

3
drivers/gpu/drm/nouveau/nouveau_sched.c
View File

@ -413,7 +413,8 @@ 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;