Re: [PATCH V3] suspend: enable freeze timeout configuration throughsys
From: Yasuaki Ishimatsu
Date: Thu Jan 31 2013 - 20:56:43 EST
2013/02/01 10:33, Li, Fei wrote:
-----Original Message-----
From: Rafael J. Wysocki [mailto:rjw@xxxxxxx]
Sent: Friday, February 01, 2013 6:29 AM
To: anish singh; Li, Fei
Cc: Yasuaki Ishimatsu; akpm@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
linux-pm@xxxxxxxxxxxxxxx; Liu, Chuansheng
Subject: Re: [PATCH V3] suspend: enable freeze timeout configuration through
sys
On Thursday, January 31, 2013 03:22:25 PM anish singh wrote:
On Thu, Jan 31, 2013 at 2:43 PM, Li, Fei <fei.li@xxxxxxxxx> wrote:
-----Original Message-----
From: Yasuaki Ishimatsu [mailto:isimatu.yasuaki@xxxxxxxxxxxxxx]
Sent: Thursday, January 31, 2013 3:30 PM
To: Li, Fei
Cc: rjw@xxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
linux-pm@xxxxxxxxxxxxxxx; Liu, Chuansheng
Subject: Re: [PATCH V3] suspend: enable freeze timeout configuration
through
sys
2013/01/31 13:55, fli24 wrote:
At present, the value of timeout for freezing is 20s, which is
meaningless in case that one thread is frozen with mutex locked
and another thread is trying to lock the mutex, as this time of
freezing will fail unavoidably.
And if there is no new wakeup event registered, the system will
waste at most 20s for such meaningless trying of freezing.
With this patch, the value of timeout can be configured to smaller
value, so such meaningless trying of freezing will be aborted in
earlier time, and later freezing can be also triggered in earlier
time. And more power will be saved.
In normal case on mobile phone, it costs real little time to freeze
processes. On some platform, it only costs about 20ms to freeze
user space processes and 10ms to freeze kernel freezable threads.
Signed-off-by: Liu Chuansheng <chuansheng.liu@xxxxxxxxx>
Signed-off-by: Li Fei <fei.li@xxxxxxxxx>
---
Documentation/power/freezing-of-tasks.txt | 5 +++++
include/linux/freezer.h | 5 +++++
kernel/power/main.c | 27
+++++++++++++++++++++++++++
kernel/power/process.c | 4 ++--
4 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/Documentation/power/freezing-of-tasks.txt
b/Documentation/power/freezing-of-tasks.txt
index 6ec291e..85894d8 100644
--- a/Documentation/power/freezing-of-tasks.txt
+++ b/Documentation/power/freezing-of-tasks.txt
@@ -223,3 +223,8 @@ since they ask the freezer to skip freezing this
task,
since it is anyway
only after the entire suspend/hibernation sequence is complete.
So, to summarize, use [un]lock_system_sleep() instead of directly using
mutex_[un]lock(&pm_mutex). That would prevent freezing failures.
+
+V. Miscellaneous
+/sys/power/pm_freeze_timeout controls how long it will cost at most to
freeze
+all user space processes or all freezable kernel threads, in unit of
millisecond.
+The default value is 20000, with range of unsigned integer.
diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index e4238ce..5a24a33 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -13,6 +13,11 @@ extern bool pm_freezing; /* PM
freezing in effect
*/
extern bool pm_nosig_freezing; /* PM nosig freezing in
effect */
/*
+ * Timeout for stopping processes
+ */
+extern unsigned int sys_freeze_process_timeout_msecs;
+
+/*
* Check if a process has been frozen
*/
static inline bool frozen(struct task_struct *p)
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 1c16f91..453ead1 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -553,6 +553,30 @@ power_attr(pm_trace_dev_match);
#endif /* CONFIG_PM_TRACE */
+#ifdef CONFIG_FREEZER
+static ssize_t pm_freeze_timeout_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char
*buf)
+{
+ return sprintf(buf, "%u\n", sys_freeze_process_timeout_msecs);
+}
+
+static ssize_t pm_freeze_timeout_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ unsigned long val;
+
+ if (kstrtoul(buf, 10, &val))
+ return -EINVAL;
+
+ sys_freeze_process_timeout_msecs = val;
+ return n;
+}
+
+power_attr(pm_freeze_timeout);
+
+#endif /* CONFIG_FREEZER*/
+
static struct attribute * g[] = {
&state_attr.attr,
#ifdef CONFIG_PM_TRACE
@@ -576,6 +600,9 @@ static struct attribute * g[] = {
&pm_print_times_attr.attr,
#endif
#endif
+#ifdef CONFIG_FREEZER
+ &pm_freeze_timeout_attr.attr,
+#endif
NULL,
};
diff --git a/kernel/power/process.c b/kernel/power/process.c
index d5a258b..ba45a26 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -21,7 +21,7 @@
/*
* Timeout for stopping processes
*/
-#define TIMEOUT (20 * HZ)
+unsigned int __read_mostly sys_freeze_process_timeout_msecs =
20000;
20000 does not mean 20 seconds since we can select HZ other than 1000.
So (20 * HZ) is better than 20000.
[Li, Fei]
Are you sure about this, (20*HZ) better than 20000, or you mean 20 *
MSEC_PER_SEC?
Yasuaki mean HZ value will not always be 1000.The value of HZ differs for
each
supported architecture. In fact, on some supported architectures,
it even differs between machine types.
When writing kernel code, never assume that HZ has any given value.
Right now you are assuming that the delay will be always 20 seconds because
of
your assumption of HZ.
That's correct, the initial value should be 20 * HZ (i.e. as before).
[Li, Fei]
Yes, you are right, and IMHO it's already as this in the patch,
as 20 * HZ == msecs_to_jiffies(20000), with the current definition MSEC_PER_SEC
of 1000L. I'll update the default value as 20 * MSEC_PER_SEC in patch V4.
20 * MSEC_PER_SEC is not 20 seconds. In Linux, 1 * HZ is 1 seconds.
Thus,
- If HZ is defined as 1000, 1000 is 1 seconds.
- If HZ is defined as 250, 250 is 1 seconds.
20 * MSEC_PER_SEC is always 20000.
Thus,
- If HZ is defined as 1000, 20 * MSEC_PER_SEC is 20 seconds.
- If HZ is defined as 250, 20 * MSEC_PER_SEC is 80 seconds.
So you should use 20 * HZ if you define timeout at 20 seconds.
Thanks,
Yasuaki Ishimatsu.
Besides, the name of the variable doesn't need to be _that_ long.
What about freeze_timeout_msecs?
[Li, Fei]
Agree with you, and will update it in patch V4.
Thanks and Regards,
Li Fei
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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