linux-kernel - [PATCH 2/2] drm/xe: WQ_PERCPU added to alloc

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Message-ID: <20251031105939.129200-3-marco.crivellari@suse.com>
Date: Fri, 31 Oct 2025 11:59:39 +0100
From: Marco Crivellari <marco.crivellari@...e.com>
To: linux-kernel@...r.kernel.org,
	intel-xe@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org
Cc: Tejun Heo <tj@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Marco Crivellari <marco.crivellari@...e.com>,
	Michal Hocko <mhocko@...e.com>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Thomas Hellstrom <thomas.hellstrom@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
Subject: [PATCH 2/2] drm/xe: WQ_PERCPU added to alloc_workqueue users

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@...nel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
---
 drivers/gpu/drm/xe/xe_device.c          | 4 ++--
 drivers/gpu/drm/xe/xe_ggtt.c            | 2 +-
 drivers/gpu/drm/xe/xe_hw_engine_group.c | 3 ++-
 drivers/gpu/drm/xe/xe_sriov.c           | 2 +-
 4 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 2883b39c9b37..2ad633abf3b2 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -486,8 +486,8 @@ struct xe_device *xe_device_create(struct pci_dev *pdev,
 	xe->preempt_fence_wq = alloc_ordered_workqueue("xe-preempt-fence-wq",
 						       WQ_MEM_RECLAIM);
 	xe->ordered_wq = alloc_ordered_workqueue("xe-ordered-wq", 0);
-	xe->unordered_wq = alloc_workqueue("xe-unordered-wq", 0, 0);
-	xe->destroy_wq = alloc_workqueue("xe-destroy-wq", 0, 0);
+	xe->unordered_wq = alloc_workqueue("xe-unordered-wq", WQ_PERCPU, 0);
+	xe->destroy_wq = alloc_workqueue("xe-destroy-wq", WQ_PERCPU, 0);
 	if (!xe->ordered_wq || !xe->unordered_wq ||
 	    !xe->preempt_fence_wq || !xe->destroy_wq) {
 		/*
diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
index 7fdd0a97a628..84466be244ab 100644
--- a/drivers/gpu/drm/xe/xe_ggtt.c
+++ b/drivers/gpu/drm/xe/xe_ggtt.c
@@ -291,7 +291,7 @@ int xe_ggtt_init_early(struct xe_ggtt *ggtt)
 	else
 		ggtt->pt_ops = &xelp_pt_ops;
 
-	ggtt->wq = alloc_workqueue("xe-ggtt-wq", 0, WQ_MEM_RECLAIM);
+	ggtt->wq = alloc_workqueue("xe-ggtt-wq", WQ_PERCPU, WQ_MEM_RECLAIM);
 	__xe_ggtt_init_early(ggtt, xe_wopcm_size(xe));
 
 	err = drmm_add_action_or_reset(&xe->drm, ggtt_fini_early, ggtt);
diff --git a/drivers/gpu/drm/xe/xe_hw_engine_group.c b/drivers/gpu/drm/xe/xe_hw_engine_group.c
index fa4db5f23342..8526addcdf42 100644
--- a/drivers/gpu/drm/xe/xe_hw_engine_group.c
+++ b/drivers/gpu/drm/xe/xe_hw_engine_group.c
@@ -48,7 +48,8 @@ hw_engine_group_alloc(struct xe_device *xe)
 	if (!group)
 		return ERR_PTR(-ENOMEM);
 
-	group->resume_wq = alloc_workqueue("xe-resume-lr-jobs-wq", 0, 0);
+	group->resume_wq = alloc_workqueue("xe-resume-lr-jobs-wq", WQ_PERCPU,
+					   0);
 	if (!group->resume_wq)
 		return ERR_PTR(-ENOMEM);
 
diff --git a/drivers/gpu/drm/xe/xe_sriov.c b/drivers/gpu/drm/xe/xe_sriov.c
index 7d2d6de2aabf..5c36da17f745 100644
--- a/drivers/gpu/drm/xe/xe_sriov.c
+++ b/drivers/gpu/drm/xe/xe_sriov.c
@@ -120,7 +120,7 @@ int xe_sriov_init(struct xe_device *xe)
 		xe_sriov_vf_init_early(xe);
 
 	xe_assert(xe, !xe->sriov.wq);
-	xe->sriov.wq = alloc_workqueue("xe-sriov-wq", 0, 0);
+	xe->sriov.wq = alloc_workqueue("xe-sriov-wq", WQ_PERCPU, 0);
 	if (!xe->sriov.wq)
 		return -ENOMEM;
 
-- 
2.51.0