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Subject[PATCH 2/3] mm: replace use of system_wq with system_percpu_wq
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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.

system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users.
Make it clear by adding a system_percpu_wq to all the mm subsystem.

The old wq will be kept for a few release cylces.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
mm/backing-dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index e9f9fdcfe052..7e672424f928 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -966,7 +966,7 @@ static int __init cgwb_init(void)
{
/*
* There can be many concurrent release work items overwhelming
- * system_wq. Put them in a separate wq and limit concurrency.
+ * system_percpu_wq. Put them in a separate wq and limit concurrency.
* There's no point in executing many of these in parallel.
*/
cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
--
2.51.0

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