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Subject: Re: [Ocfs2-devel] [PATCH 1/2] ocfs2: add last unlock times in
 locking_state
To:     Gang He <ghe@suse.com>, mark@fasheh.com, jlbec@evilplan.org,
        jiangqi903@gmail.com
Cc:     linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com
References: <20190523104047.14794-1-ghe@suse.com>
From:   Wengang <wen.gang.wang@oracle.com>
Message-ID: <66083663-1d25-437b-ce98-07d200f446ab@oracle.com>
Date:   Tue, 28 May 2019 10:22:30 -0700
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Hi Gang,

This idea sounds cool!
Some comments in lines:

On 05/23/2019 03:40 AM, Gang He wrote:
> ocfs2 file system uses locking_state file under debugfs to dump
> each ocfs2 file system's dlm lock resources, but the dlm lock
> resources in memory are becoming more and more after the files
> were touched by the user. it will become a bit difficult to analyze
> these dlm lock resource records in locking_state file by the upper
> scripts, though some files are not active for now, which were
> accessed long time ago.
> Then, I'd like to add last pr/ex unlock times in locking_state file
> for each dlm lock resource record, the the upper scripts can use
> last unlock time to filter inactive dlm lock resource record.
>
> Signed-off-by: Gang He <ghe@suse.com>
> Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> ---
>   fs/ocfs2/dlmglue.c | 21 +++++++++++++++++----
>   fs/ocfs2/ocfs2.h   |  1 +
>   2 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
> index af405586c5b1..dccf4136f8c1 100644
> --- a/fs/ocfs2/dlmglue.c
> +++ b/fs/ocfs2/dlmglue.c
> @@ -448,7 +448,7 @@ static void ocfs2_update_lock_stats(struct ocfs2_lock_res *res, int level,
>   				    struct ocfs2_mask_waiter *mw, int ret)
>   {
>   	u32 usec;
> -	ktime_t kt;
> +	ktime_t last, kt;
>   	struct ocfs2_lock_stats *stats;
>   
>   	if (level == LKM_PRMODE)
> @@ -458,7 +458,8 @@ static void ocfs2_update_lock_stats(struct ocfs2_lock_res *res, int level,
>   	else
>   		return;
>   
> -	kt = ktime_sub(ktime_get(), mw->mw_lock_start);
> +	last = ktime_get();
Will ktime_get_real() be better than ktime_get() here?
Per description,
ktime_get:
Useful for reliable timestamps and measuring short time intervals 
accurately. Starts at system boot time but stops during suspend.
ktime_get_real:
Returns the time in relative to the UNIX epoch starting in 1970 using 
the Coordinated Universal Time (UTC), same as gettimeofday() user space.

Since ktime_get() returnis time since boot time, this value is 
meaningless when compared to those from a different node in cluster, right?

And we need a "__kernel_long_t" to rather than a "u32"?


> +	kt = ktime_sub(last, mw->mw_lock_start);
>   	usec = ktime_to_us(kt);
>   
>   	stats->ls_gets++;
> @@ -474,6 +475,8 @@ static void ocfs2_update_lock_stats(struct ocfs2_lock_res *res, int level,
>   
>   	if (ret)
>   		stats->ls_fail++;
> +
> +	stats->ls_last = ktime_to_timespec(last).tv_sec;
>   }
>   
Though maybe ocfs2_update_lock_stats() is designed to be called for each 
successful lock request,
seems current code calls it even when it returns with -EAGAIN which 
breaks the design.  That's not introduced by your change, well, it may 
lead to wrong stats...

thanks,
wengang

>   static inline void ocfs2_track_lock_refresh(struct ocfs2_lock_res *lockres)
> @@ -3093,8 +3096,10 @@ static void *ocfs2_dlm_seq_next(struct seq_file *m, void *v, loff_t *pos)
>    *	- Lock stats printed
>    * New in version 3
>    *	- Max time in lock stats is in usecs (instead of nsecs)
> + * New in version 4
> + *	- Add last pr/ex unlock times in secs
>    */
> -#define OCFS2_DLM_DEBUG_STR_VERSION 3
> +#define OCFS2_DLM_DEBUG_STR_VERSION 4
>   static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
>   {
>   	int i;
> @@ -3145,6 +3150,8 @@ static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
>   # define lock_max_prmode(_l)		((_l)->l_lock_prmode.ls_max)
>   # define lock_max_exmode(_l)		((_l)->l_lock_exmode.ls_max)
>   # define lock_refresh(_l)		((_l)->l_lock_refresh)
> +# define lock_last_prmode(_l)		((_l)->l_lock_prmode.ls_last)
> +# define lock_last_exmode(_l)		((_l)->l_lock_exmode.ls_last)
>   #else
>   # define lock_num_prmode(_l)		(0)
>   # define lock_num_exmode(_l)		(0)
> @@ -3155,6 +3162,8 @@ static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
>   # define lock_max_prmode(_l)		(0)
>   # define lock_max_exmode(_l)		(0)
>   # define lock_refresh(_l)		(0)
> +# define lock_last_prmode(_l)		(0)
> +# define lock_last_exmode(_l)		(0)
>   #endif
>   	/* The following seq_print was added in version 2 of this output */
>   	seq_printf(m, "%u\t"
> @@ -3165,6 +3174,8 @@ static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
>   		   "%llu\t"
>   		   "%u\t"
>   		   "%u\t"
> +		   "%u\t"
> +		   "%u\t"
>   		   "%u\t",
>   		   lock_num_prmode(lockres),
>   		   lock_num_exmode(lockres),
> @@ -3174,7 +3185,9 @@ static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
>   		   lock_total_exmode(lockres),
>   		   lock_max_prmode(lockres),
>   		   lock_max_exmode(lockres),
> -		   lock_refresh(lockres));
> +		   lock_refresh(lockres),
> +		   lock_last_prmode(lockres),
> +		   lock_last_exmode(lockres));
>   
>   	/* End the line */
>   	seq_printf(m, "\n");
> diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
> index 1f029fbe8b8d..8efa022684f4 100644
> --- a/fs/ocfs2/ocfs2.h
> +++ b/fs/ocfs2/ocfs2.h
> @@ -164,6 +164,7 @@ struct ocfs2_lock_stats {
>   
>   	/* Storing max wait in usecs saves 24 bytes per inode */
>   	u32		ls_max;		/* Max wait in USEC */
> +	u32		ls_last;	/* Last unlock time in SEC */
>   };
>   #endif
>