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Marco Crivellari a8980af1bf virtio_balloon: add WQ_PERCPU to alloc_workqueue users
Currently if a user enqueues 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.

alloc_workqueue() treats all queues as per-CPU by default, while unbound
workqueues must opt-in via WQ_UNBOUND.

This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.

This continues the effort to refactor workqueue APIs, which began with
the introduction of new workqueues and a new alloc_workqueue flag in:

commit 128ea9f6cc ("workqueue: Add system_percpu_wq and system_dfl_wq")
commit 930c2ea566 ("workqueue: Add new WQ_PERCPU flag")

This change adds a new WQ_PERCPU flag to explicitly request
alloc_workqueue() to be per-cpu when WQ_UNBOUND has not been specified.

With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.

Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251107154917.313090-2-marco.crivellari@suse.com>
History 2025-11-27 02:03:07 -05:00
arch Fix perf CPU-clock counters, and address a static checker warning. 2025-11-23 08:20:15 -08:00
block vfs-6.18-rc7.fixes 2025-11-17 09:11:27 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push contains the following changes: 2025-10-10 08:56:16 -07:00
Documentation Input updates for v6.18-rc6 2025-11-22 09:58:41 -08:00
drivers virtio_balloon: add WQ_PERCPU to alloc_workqueue users 2025-11-27 02:03:07 -05:00
fs xfs: fixes for 6.18-rc7 2025-11-22 10:23:34 -08:00
include virtio: fix map ops comment 2025-11-27 02:03:06 -05:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/cmd_net: fix wrong argument types for skb_queue_splice() 2025-11-20 11:40:15 -07:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel Miscellaneous fixes: 2025-11-23 08:23:30 -08:00
lib Crypto library fix for v6.18-rc7 2025-11-22 11:53:53 -08:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab fix for 6.18-rc7 2025-11-20 10:49:12 -08:00
net Including fixes from IPsec and wireless. 2025-11-20 08:52:07 -08:00
rust rust: Add -fno-isolate-erroneous-paths-dereference to bindgen_skip_c_flags 2025-11-10 08:37:06 +08:00
samples samples: work around glibc redefining some of our defines wrong 2025-11-21 09:29:02 -08:00
scripts Rust fixes for v6.18 (2nd) 2025-11-14 15:36:15 -08:00
security selinux/stable-6.18 PR 20251121 2025-11-22 09:24:36 -08:00
sound ALSA: usb-audio: Add native DSD quirks for PureAudio DAC series 2025-11-14 14:19:47 +01:00
tools RISC-V updates for v6.18-rc7 2025-11-22 09:44:50 -08:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying 2025-11-04 09:16:53 -08:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap soc: fixes for 6.18, part 3 2025-11-19 09:36:04 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS gpio fixes for v6.18-rc7 2025-11-21 10:43:58 -08:00
Makefile Linux 6.18-rc7 2025-11-23 14:53:16 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.