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 1-2] Replace uses of system_wq and system_unbound_wq
system_wq is a per-CPU workqueue, but his name is not clear.
system_unbound_wq is to be used when locality is not required.
Because of that, system_wq has been replaced with system_percpu_wq, and
system_unbound_wq has been replaced with system_dfl_wq.
2) [P 3] 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!
---
Changes in 3:
- Improved commit logs
Changes in v2:
- fix typo in patch subject (add instead of added).
- in every patch is also present the specific commit hash about the
workqueue API change.
- fixed commit log of P1 (removed "Adding system_dfl_wq...").
- P2: subject changed reflecting the effective change.
- rebased to v6.18-rc4.
Marco Crivellari (3):
drm/i915: replace use of system_unbound_wq with system_dfl_wq
drm/i915: replace use of system_wq with system_percpu_wq in the
documentation
drm/i915: add WQ_PERCPU to alloc_workqueue users
drivers/gpu/drm/i915/display/intel_display_driver.c | 4 ++--
drivers/gpu/drm/i915/display/intel_display_power.c | 2 +-
drivers/gpu/drm/i915/display/intel_tc.c | 4 ++--
drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 2 +-
drivers/gpu/drm/i915/gt/uc/intel_guc.c | 4 ++--
drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 4 ++--
drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 6 +++---
drivers/gpu/drm/i915/i915_active.c | 2 +-
drivers/gpu/drm/i915/i915_driver.c | 5 +++--
drivers/gpu/drm/i915/i915_drv.h | 2 +-
drivers/gpu/drm/i915/i915_sw_fence_work.c | 2 +-
drivers/gpu/drm/i915/i915_vma_resource.c | 2 +-
drivers/gpu/drm/i915/pxp/intel_pxp.c | 2 +-
drivers/gpu/drm/i915/pxp/intel_pxp_irq.c | 2 +-
drivers/gpu/drm/i915/selftests/i915_sw_fence.c | 2 +-
drivers/gpu/drm/i915/selftests/mock_gem_device.c | 2 +-
16 files changed, 24 insertions(+), 23 deletions(-)
--
2.51.1
