linux-kernel - [PATCH v4 2/3] workqueue: doc: Add a note saturating the system

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Message-ID: <20240913131720.1762188-3-chenridong@huawei.com>
Date: Fri, 13 Sep 2024 13:17:19 +0000
From: Chen Ridong <chenridong@...wei.com>
To: <martin.lau@...ux.dev>, <ast@...nel.org>, <daniel@...earbox.net>,
	<andrii@...nel.org>, <eddyz87@...il.com>, <song@...nel.org>,
	<yonghong.song@...ux.dev>, <john.fastabend@...il.com>, <kpsingh@...nel.org>,
	<sdf@...gle.com>, <haoluo@...gle.com>, <jolsa@...nel.org>, <tj@...nel.org>,
	<lizefan.x@...edance.com>, <hannes@...xchg.org>, <roman.gushchin@...ux.dev>
CC: <bpf@...r.kernel.org>, <cgroups@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH v4 2/3] workqueue: doc: Add a note saturating the system_wq is not permitted

If something is expected to generate large number of concurrent works,
it should utilize its own dedicated workqueue rather than system wq.
Because this may saturate system_wq and potentially block other's works.
eg, cgroup release work. Let's document this as a note.

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 Documentation/core-api/workqueue.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/core-api/workqueue.rst b/Documentation/core-api/workqueue.rst
index 16f861c9791e..338b25e86f8c 100644
--- a/Documentation/core-api/workqueue.rst
+++ b/Documentation/core-api/workqueue.rst
@@ -356,6 +356,10 @@ Guidelines
   special attribute, can use one of the system wq.  There is no
   difference in execution characteristics between using a dedicated wq
   and a system wq.
+  Note: If something is expected to generate large number of concurrent
+  works, it should utilize its own dedicated workqueue rather than
+  system wq. Because this may saturate system_wq and potentially block
+  other's works. eg, cgroup release work.
 
 * Unless work items are expected to consume a huge amount of CPU
   cycles, using a bound wq is usually beneficial due to the increased
-- 
2.34.1