diff options
| author | Marco Crivellari <marco.crivellari@suse.com> | 2025-09-05 11:05:33 +0200 |
|---|---|---|
| committer | Herbert Xu <herbert@gondor.apana.org.au> | 2025-09-13 12:11:06 +0800 |
| commit | 4fcd322914068f2c6aec7bb5cfd12ce0207b3a21 (patch) | |
| tree | 83181f6c4fe28138b18dd2855a7fe8a391972943 | |
| parent | b6d02e0e41aa87aaa46b9b995e71a585284c5d27 (diff) | |
padata: WQ_PERCPU added to alloc_workqueue users
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 consistentcy 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 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 patch adds a new WQ_PERCPU flag to explicitly request the use of
the per-CPU behavior. Both flags coexist for one release cycle to allow
callers to transition their calls.
Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.
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.
All existing users have been updated accordingly.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
| -rw-r--r-- | kernel/padata.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/padata.c b/kernel/padata.c index d7cc95367209..f4def028c48c 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -967,8 +967,9 @@ struct padata_instance *padata_alloc(const char *name) cpus_read_lock(); - pinst->serial_wq = alloc_workqueue("%s_serial", WQ_MEM_RECLAIM | - WQ_CPU_INTENSIVE, 1, name); + pinst->serial_wq = alloc_workqueue("%s_serial", + WQ_MEM_RECLAIM | WQ_CPU_INTENSIVE | WQ_PERCPU, + 1, name); if (!pinst->serial_wq) goto err_put_cpus; |