linux-kernel - [RFC PATCH v1 8/9] freezer: Add retry count statistics for freeze pass iterations

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Message-Id: <20250807121418.139765-9-zhangzihuan@kylinos.cn>
Date: Thu,  7 Aug 2025 20:14:17 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	David Hildenbrand <david@...hat.com>,
	Michal Hocko <mhocko@...e.com>,
	Jonathan Corbet <corbet@....net>
Cc: Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
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	len brown <len.brown@...el.com>,
	pavel machek <pavel@...nel.org>,
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	Christian Brauner <brauner@...nel.org>,
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	Al Viro <viro@...iv.linux.org.uk>,
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	linux-pm@...r.kernel.org,
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	Zihuan Zhang <zhangzihuan@...inos.cn>
Subject: [RFC PATCH v1 8/9] freezer: Add retry count statistics for freeze pass iterations

Freezer retry loops during suspend are often triggered by tasks entering
D-state (TASK_UNINTERRUPTIBLE), which cannot be frozen.  This patch adds
a simple retry counter to freeze_processes() to help quantify how many
attempts were required before all tasks entered the frozen state. This
is useful for performance tuning and debugging unpredictable suspend
delays.

A new dmesg log is added for visibility:

freeze round: xx, tasks to freeze: xx

This message allows users to correlate freeze instability with system
state.

Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>
---
 kernel/power/process.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/power/process.c b/kernel/power/process.c
index 9d3cbde905b9..442d2ebba3ed 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -76,6 +76,8 @@ static int try_to_freeze_tasks(bool user_only)
 		if (user_only && !has_freezable_task)
 			continue;
 
+		pr_info("freeze round: %d, task to freeze: %d\n", round, todo);
+
 		if (!todo || time_after(jiffies, end_time))
 			break;
 
-- 
2.25.1