mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-12-27 14:41:22 -05:00
e360bb6dc8
Marco Crivellari <marco.crivellari@suse.com> says: 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: - commit128ea9f6cc("workqueue: Add system_percpu_wq and system_dfl_wq") - commit930c2ea566("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 clear it should be used when locality is not required. 2) [P 2-3-4] 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! Link: https://patch.msgid.link/20251031095643.74246-1-marco.crivellari@suse.com Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.