linux-kernel - Re: [PATCH v5] PM / sleep: measure the time of filesystem syncing

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Date:   Fri, 22 Feb 2019 18:54:44 +0100
From:   Pavel Machek <pavel@....cz>
To:     Harry Pan <harry.pan@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, gs0622@...il.com,
        rjw@...ysocki.net, len.brown@...el.com, linux-pm@...r.kernel.org
Subject: Re: [PATCH v5] PM / sleep: measure the time of filesystem syncing

On Fri 2019-02-22 23:49:04, Harry Pan wrote:
> This patch gives the reader an intuitive metric of the time cost by
> the kernel issuing a filesystem sync during system sleep; although
> developer can guess by the timestamp of next log or enable the ftrace
> power event for manual calculation, this manner is easier to read and
> benefits the automatic script.
> 
> v2: simplify the variables, apply the simplest form of ktime API.
> v3: reduce conditional compilation, rectify profiling in better syntax
> v4: avoid interposition, profile on hibernation, rectify printk format
> v5: introduce sync helper shared by suspend, hibernate, and snapshot
> 
> Signed-off-by: Harry Pan <harry.pan@...el.com>
> ---
>  include/linux/suspend.h  |  3 +++
>  kernel/power/hibernate.c |  5 +----
>  kernel/power/main.c      | 15 +++++++++++++++
>  kernel/power/suspend.c   | 13 +++++--------
>  kernel/power/user.c      |  5 +----
>  5 files changed, 25 insertions(+), 16 deletions(-)
> 
> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
> index 3f529ad9a9d2..6b3ea9ea6a9e 100644
> --- a/include/linux/suspend.h
> +++ b/include/linux/suspend.h
> @@ -425,6 +425,7 @@ void restore_processor_state(void);
>  /* kernel/power/main.c */
>  extern int register_pm_notifier(struct notifier_block *nb);
>  extern int unregister_pm_notifier(struct notifier_block *nb);
> +extern void ksys_sync_helper(void);
>  
>  #define pm_notifier(fn, pri) {				\
>  	static struct notifier_block fn##_nb =			\
> @@ -462,6 +463,8 @@ static inline int unregister_pm_notifier(struct notifier_block *nb)
>  	return 0;
>  }
>  
> +static inline void ksys_sync_helper(void) {}
> +
>  #define pm_notifier(fn, pri)	do { (void)(fn); } while (0)
>  
>  static inline bool pm_wakeup_pending(void) { return false; }
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index abef759de7c8..cc105ecd9c07 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -14,7 +14,6 @@
>  
>  #include <linux/export.h>
>  #include <linux/suspend.h>
> -#include <linux/syscalls.h>
>  #include <linux/reboot.h>
>  #include <linux/string.h>
>  #include <linux/device.h>
> @@ -709,9 +708,7 @@ int hibernate(void)
>  		goto Exit;
>  	}
>  
> -	pr_info("Syncing filesystems ... \n");
> -	ksys_sync();
> -	pr_info("done.\n");
> +	ksys_sync_helper();
>  
>  	error = freeze_processes();
>  	if (error)
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index 35b50823d83b..a08dcc743f31 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -16,6 +16,7 @@
>  #include <linux/debugfs.h>
>  #include <linux/seq_file.h>
>  #include <linux/suspend.h>
> +#include <linux/syscalls.h>
>  
>  #include "power.h"
>  
> @@ -51,6 +52,20 @@ void unlock_system_sleep(void)
>  }
>  EXPORT_SYMBOL_GPL(unlock_system_sleep);
>  
> +void ksys_sync_helper(void)
> +{
> +	ktime_t start;
> +	s64 elapsed_msecs;
> +
> +	start = ktime_get();
> +	ksys_sync();
> +	elapsed_msecs = ktime_to_ms(ktime_sub(ktime_get(), start));
> +	pr_info("Filesystems sync: %lld.%03lld seconds\n",
> +		elapsed_msecs / MSEC_PER_SEC,
> +		elapsed_msecs % MSEC_PER_SEC);
> +}

Sharing code is fine. Changing message, remove partial print before
long operation is not.

Adding timing is not, either. There are other ways to get that info.

NAK.
									Pavel
								
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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