[PATCH net-next v4 0/6] net: Move system_long_wq to system_dfl_long_wq

Hello,

This is only rebased as it seems the patches didn't land in the next
release because are marked as Rejected (likely because of initial feedback
on 5/6),despite the general positive overall feedbacks (also on Patch 5/6,
later):

  https://lore.kernel.org/all/20260906080818.GC6356@carbon.k.g/ (local)

---

Currently the code uses the per-cpu workqueue system_long_wq to schedule
long running works.

Unbound works could benefit from scheduler task placement, to optimize
performance and power consumption. Another good reason to have this unbound,
is the "queue_delayed_work()" function, used to enqueue the work item.
More details on this will follow in the next section.

Recently, a new unbound workqueue specific for long running work has been
added:

    c116737e972e ("workqueue: Add system_dfl_long_wq for long unbound works")

~~~ Details about queue_delayed_work ~~~

system_long_wq is a per-cpu workqueue and it is used as a parameter of
queue_delayed_work(). This function schedule an item that it will later
be enqueued (once the timer will fire). __queue_delayed_work() does the job
receiving as "cpu" WORK_CPU_UNBOUND:

    if (housekeeping_enabled(HK_TYPE_TIMER)) {
    //      [....]
    } else {
            if (likely(cpu == WORK_CPU_UNBOUND))
                    add_timer_global(timer);
            else
                    add_timer_on(timer, cpu);
    }

The timer is global, so can fire everywhere, and the work item will be
enqueued where the timer fired.

Since the workqueue work doesn't rely on per-cpu variables, there is no
obvious reason that justify the use of a per-cpu workqueue. So change the
workqueue with the new system_dfl_long_wq, so that the used workqueue is
now unbound and can benefit from scheduler task placement.

Thanks!

---
Changes in v4:
- rebased on v7.3-rc7

- added review-by Sebastian on 5/6

Link to v3: https://lore.kernel.org/all/20260720100902.155605-1-marco.crivellari@suse.com/ (local)

Changes in v3:
- rebased on v7.2-rc4

- added "net: ti: icssg-prueth: Move long delayed work on system_dfl_long_wq"

- changed also the workqueue in ibmvnic_reset().

Link to v2: https://lore.kernel.org/all/20260706134033.244295-1-marco.crivellari@suse.com/ (local)

Changes in v2:
- rebased on v7.2-rc2

- dropped the RFC prefix, kept Ack and review tags

Link to v1: https://lore.kernel.org/all/20260511092846.120141-1-marco.crivellari@suse.com/ (local)

Marco Crivellari (6):
  ibmvnic: Move long delayed work on system_dfl_long_wq
  net: ti: icssg-stats: Move long delayed work on system_dfl_long_wq
  net: ti: icssg-prueth: Move long delayed work on system_dfl_long_wq
  net: thunderbolt: Move long delayed work on system_dfl_long_wq
  net: usb: pegasus: Move long delayed work on system_dfl_long_wq
  net: usb: r8152: Move long delayed work on system_dfl_long_wq

 drivers/net/ethernet/ibm/ibmvnic.c           | 6 +++---
 drivers/net/ethernet/ti/icssg/icssg_prueth.c | 2 +-
 drivers/net/ethernet/ti/icssg/icssg_stats.c  | 2 +-
 drivers/net/thunderbolt/main.c               | 7 ++++---
 drivers/net/usb/pegasus.c                    | 9 +++++----
 drivers/net/usb/r8152.c                      | 7 ++++---
 6 files changed, 18 insertions(+), 15 deletions(-)

-- 
2.55.0