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_wq and 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 sure it is the default choice when locality
    is not important.

    system_dfl_wq has the same behavior of the old system_unbound_wq.

2) [P 2-5] 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 (5):
  RDMA/core: RDMA/mlx5: replace use of system_unbound_wq with
    system_dfl_wq
  RDMA/core: WQ_PERCPU added to alloc_workqueue users
  hfi1: WQ_PERCPU added to alloc_workqueue users
  RDMA/mlx4: WQ_PERCPU added to alloc_workqueue users
  IB/rdmavt: WQ_PERCPU added to alloc_workqueue users

 drivers/infiniband/core/cm.c      | 2 +-
 drivers/infiniband/core/device.c  | 4 ++--
 drivers/infiniband/core/ucma.c    | 2 +-
 drivers/infiniband/hw/hfi1/init.c | 4 ++--
 drivers/infiniband/hw/hfi1/opfn.c | 4 ++--
 drivers/infiniband/hw/mlx4/cm.c   | 2 +-
 drivers/infiniband/hw/mlx5/odp.c  | 4 ++--
 drivers/infiniband/sw/rdmavt/cq.c | 3 ++-
 8 files changed, 13 insertions(+), 12 deletions(-)

-- 
2.51.0

Hi,

On Sat, Nov 1, 2025 at 5:31 PM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> Marco Crivellari (5):
>   RDMA/core: RDMA/mlx5: replace use of system_unbound_wq with
>     system_dfl_wq
>   RDMA/core: WQ_PERCPU added to alloc_workqueue users
>   hfi1: WQ_PERCPU added to alloc_workqueue users
>   RDMA/mlx4: WQ_PERCPU added to alloc_workqueue users
>   IB/rdmavt: WQ_PERCPU added to alloc_workqueue users
>
>  drivers/infiniband/core/cm.c      | 2 +-
>  drivers/infiniband/core/device.c  | 4 ++--
>  drivers/infiniband/core/ucma.c    | 2 +-
>  drivers/infiniband/hw/hfi1/init.c | 4 ++--
>  drivers/infiniband/hw/hfi1/opfn.c | 4 ++--
>  drivers/infiniband/hw/mlx4/cm.c   | 2 +-
>  drivers/infiniband/hw/mlx5/odp.c  | 4 ++--
>  drivers/infiniband/sw/rdmavt/cq.c | 3 ++-
>  8 files changed, 13 insertions(+), 12 deletions(-)

Gentle ping.

Thanks!

-- 

Marco Crivellari

L3 Support Engineer, Technology & Product

On Tue, Dec 02, 2025 at 02:22:55PM +0100, Marco Crivellari wrote:
> Hi,
> 
> On Sat, Nov 1, 2025 at 5:31 PM Marco Crivellari
> <marco.crivellari@suse.com> wrote:
> > Marco Crivellari (5):
> >   RDMA/core: RDMA/mlx5: replace use of system_unbound_wq with
> >     system_dfl_wq
> >   RDMA/core: WQ_PERCPU added to alloc_workqueue users
> >   hfi1: WQ_PERCPU added to alloc_workqueue users
> >   RDMA/mlx4: WQ_PERCPU added to alloc_workqueue users
> >   IB/rdmavt: WQ_PERCPU added to alloc_workqueue users
> >
> >  drivers/infiniband/core/cm.c      | 2 +-
> >  drivers/infiniband/core/device.c  | 4 ++--
> >  drivers/infiniband/core/ucma.c    | 2 +-
> >  drivers/infiniband/hw/hfi1/init.c | 4 ++--
> >  drivers/infiniband/hw/hfi1/opfn.c | 4 ++--
> >  drivers/infiniband/hw/mlx4/cm.c   | 2 +-
> >  drivers/infiniband/hw/mlx5/odp.c  | 4 ++--
> >  drivers/infiniband/sw/rdmavt/cq.c | 3 ++-
> >  8 files changed, 13 insertions(+), 12 deletions(-)
> 
> Gentle ping.

It looks like it was picked up, the thank you email must have become lost:

5c467151f6197d IB/isert: add WQ_PERCPU to alloc_workqueue users
65d21dee533755 IB/iser: add WQ_PERCPU to alloc_workqueue users
7196156b0ce3dc IB/rdmavt: WQ_PERCPU added to alloc_workqueue users
5267feda50680c RDMA/mlx4: WQ_PERCPU added to alloc_workqueue users
5f93287fa9d0db hfi1: WQ_PERCPU added to alloc_workqueue users
e60c5583b661da RDMA/core: WQ_PERCPU added to alloc_workqueue users
f673fb3449fcd8 RDMA/core: RDMA/mlx5: replace use of system_unbound_wq with system_dfl_wq

Jason

On Tue, Dec 2, 2025 at 8:17 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> It looks like it was picked up, the thank you email must have become lost:
>
> 5c467151f6197d IB/isert: add WQ_PERCPU to alloc_workqueue users
> 65d21dee533755 IB/iser: add WQ_PERCPU to alloc_workqueue users
> 7196156b0ce3dc IB/rdmavt: WQ_PERCPU added to alloc_workqueue users
> 5267feda50680c RDMA/mlx4: WQ_PERCPU added to alloc_workqueue users
> 5f93287fa9d0db hfi1: WQ_PERCPU added to alloc_workqueue users
> e60c5583b661da RDMA/core: WQ_PERCPU added to alloc_workqueue users
> f673fb3449fcd8 RDMA/core: RDMA/mlx5: replace use of system_unbound_wq with system_dfl_wq
>
> Jason

Aha, thank you and sorry for the useless email!

-- 

Marco Crivellari

L3 Support Engineer, Technology & Product