On Fri, Sep 5, 2025 at 1:53 AM Marco Crivellari <marco.crivellari@xxxxxxxx> wrote: > > === Plan and future plans === > > This patchset is the first stone on a refactoring needed in order to > address the points aforementioned; it will have a positive impact also > on the cpu isolation, in the long term, moving away percpu workqueue in > favor to an unbound model. > > These are the main steps: > 1) API refactoring (that this patch is introducing) > - Make more clear and uniform the system wq names, both per-cpu and > unbound. This to avoid any possible confusion on what should be > used. > > - Introduction of WQ_PERCPU: this flag is the complement of WQ_UNBOUND, > introduced in this patchset and used on all the callers that are not > currently using WQ_UNBOUND. > > WQ_UNBOUND will be removed in a future release cycle. > > Most users don't need to be per-cpu, because they don't have > locality requirements, because of that, a next future step will be > make "unbound" the default behavior. > > 2) Check who really needs to be per-cpu > - Remove the WQ_PERCPU flag when is not strictly required. > > 3) Add a new API (prefer local cpu) > - There are users that don't require a local execution, like mentioned > above; despite that, local execution yeld to performance gain. > > This new API will prefer the local execution, without requiring it. > > === Introduced Changes by this series === > > 1) [P 1-2] Replace use 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 renamed in system_percpu_wq, and > system_unbound_wq has been renamed in system_dfl_wq. > > 2) [P 3] add WQ_PERCPU to remaining alloc_workqueue() users > > Every alloc_workqueue() caller should use one among WQ_PERCPU or > WQ_UNBOUND. This is actually enforced warning if both or none of them > are present at the same time. > > WQ_UNBOUND will be removed in a next release cycle. > > === For Maintainers === > > There are prerequisites for this series, already merged in the master branch. Everything makes sense. Tejun, please ack this set just to make sure it's all going as planned.
