Re: [PATCH 2/2] f2fs: add sysfs entries to select the gc policy

[Gu Zheng]

Hi Jeon,

On 07/31/2013 10:33 PM, Namjae Jeon wrote:

> From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> 
> Add sysfs entries namely gc_long_idle and gc_short_idle to control the
> gc policy. Where long idle corresponds to selecting a cost benefit approach,
> while short idle corresponds to selecting a greedy approach to garbage
> collection. The selection is mutually exclusive one approach will work at
> any point.
> 
> Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> Signed-off-by: Pankaj Kumar <pankaj.km@xxxxxxxxxxx>
> ---
>  Documentation/ABI/testing/sysfs-fs-f2fs |   12 +++++++
>  Documentation/filesystems/f2fs.txt      |    8 +++++
>  fs/f2fs/gc.c                            |   22 ++++++++++--
>  fs/f2fs/gc.h                            |    4 +++
>  fs/f2fs/super.c                         |   59 +++++++++++++++++++++++++++++--
>  5 files changed, 99 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index 5f44095..96b62ea 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -19,4 +19,16 @@ Description:
>  		 Controls the default sleep time for gc_thread. Time
>  		 is in milliseconds.
>  
> +What:		/sys/fs/f2fs/<disk>/gc_long_idle
> +Date:		July 2013
> +Contact:	"Namjae Jeon" <namjae.jeon@xxxxxxxxxxx>
> +Description:
> +		 Controls the selection of gc policy. long_idle is used
> +		 to select the cost benefit approach for garbage collection.
>  
> +What:		/sys/fs/f2fs/<disk>/gc_short_idle
> +Date:		July 2013
> +Contact:	"Namjae Jeon" <namjae.jeon@xxxxxxxxxxx>
> +Description:
> +		 Controls the selection of gc policy. short_idle is used
> +		 to select the greedy approach for garbage collection.
> diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
> index 2e9e873..06dd5d7 100644
> --- a/Documentation/filesystems/f2fs.txt
> +++ b/Documentation/filesystems/f2fs.txt
> @@ -158,6 +158,14 @@ Files in /sys/fs/f2fs/<devname>
>                                time for the garbage collection thread. Time is
>                                in milliseconds.
>  
> + gc_long_idle                 This parameter controls the selection of cost
> +                              benefit approach for garbage collectoin. Writing
> +                              1 to this file will select the cost benefit policy.
> +
> + gc_short_idle                This parameter controls the selection of greedy
> +                              approach for the garbage collection. Writing 1
> +                              to this file will select the greedy policy.

Why introduce two opposite attributes? It'll cause some confusion condition if we
double enable/disable them.

> +
>  ================================================================================
>  USAGE
>  ================================================================================
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 60d4f67..af2d9d7 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -106,6 +106,8 @@ int start_gc_thread(struct f2fs_sb_info *sbi)
>  	gc_th->max_sleep_time = DEF_GC_THREAD_MAX_SLEEP_TIME;
>  	gc_th->no_gc_sleep_time = DEF_GC_THREAD_NOGC_SLEEP_TIME;
>  
> +	gc_th->long_idle = gc_th->short_idle = 0;
> +
>  	sbi->gc_thread = gc_th;
>  	init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
>  	sbi->gc_thread->f2fs_gc_task = kthread_run(gc_thread_func, sbi,
> @@ -130,9 +132,23 @@ void stop_gc_thread(struct f2fs_sb_info *sbi)
>  	sbi->gc_thread = NULL;
>  }
>  
> -static int select_gc_type(int gc_type)
> +static int select_gc_type(struct f2fs_gc_kthread *gc_th, int gc_type)
>  {
> -	return (gc_type == BG_GC) ? GC_CB : GC_GREEDY;
> +	int gc_mode;
> +
> +	if (gc_th) {
> +		if (gc_th->long_idle) {
> +			gc_mode = GC_CB;
> +			goto out;
> +		} else if (gc_th->short_idle) {
> +			gc_mode = GC_GREEDY;
> +			goto out;
> +		}
> +	}
> +
> +	gc_mode = (gc_type == BG_GC) ? GC_CB : GC_GREEDY;
> +out:
> +	return gc_mode;
>  }
>  
>  static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
> @@ -145,7 +161,7 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
>  		p->dirty_segmap = dirty_i->dirty_segmap[type];
>  		p->ofs_unit = 1;
>  	} else {
> -		p->gc_mode = select_gc_type(gc_type);
> +		p->gc_mode = select_gc_type(sbi->gc_thread, gc_type);
>  		p->dirty_segmap = dirty_i->dirty_segmap[DIRTY];
>  		p->ofs_unit = sbi->segs_per_sec;
>  	}
> diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
> index f4bf44c..b2faae5 100644
> --- a/fs/f2fs/gc.h
> +++ b/fs/f2fs/gc.h
> @@ -30,6 +30,10 @@ struct f2fs_gc_kthread {
>  	unsigned int min_sleep_time;
>  	unsigned int max_sleep_time;
>  	unsigned int no_gc_sleep_time;
> +
> +	/* for changing gc mode */
> +	unsigned int long_idle;
> +	unsigned int short_idle;

The same issue I mentioned in the front patch, they're per f2fs sb infos.

Regards,
Gu

>  };
>  
>  struct inode_entry {
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 30de280..3db806b 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -107,6 +107,56 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>  	return count;
>  }
>  
> +static ssize_t f2fs_gc_long_idle_store(struct f2fs_attr *a,
> +			    struct f2fs_sb_info *sbi,
> +			    const char *buf, size_t count)
> +{
> +	struct f2fs_gc_kthread *gc_kth = sbi->gc_thread;
> +	unsigned long t;
> +	ssize_t ret;
> +
> +	if (!gc_kth)
> +		return -EFAULT;
> +
> +	ret = kstrtoul(skip_spaces(buf), 0, &t);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (t == 0)
> +		gc_kth->long_idle = 0;
> +	else if (t == 1) {
> +		gc_kth->long_idle = 1;
> +		gc_kth->short_idle = 0;
> +	}
> +
> +	return count;
> +}
> +
> +static ssize_t f2fs_gc_short_idle_store(struct f2fs_attr *a,
> +			    struct f2fs_sb_info *sbi,
> +			    const char *buf, size_t count)
> +{
> +	struct f2fs_gc_kthread *gc_kth = sbi->gc_thread;
> +	unsigned long t;
> +	ssize_t ret;
> +
> +	if (!gc_kth)
> +		return -EFAULT;
> +
> +	ret = kstrtoul(skip_spaces(buf), 0, &t);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (t == 0)
> +		gc_kth->short_idle = 0;
> +	else if (t == 1) {
> +		gc_kth->short_idle = 1;
> +		gc_kth->long_idle = 0;
> +	}
> +
> +	return count;
> +}
> +
>  static ssize_t f2fs_attr_show(struct kobject *kobj,
>  				struct attribute *attr, char *buf)
>  {
> @@ -142,21 +192,24 @@ static struct f2fs_attr f2fs_attr_##_name = {			\
>  	.offset = offsetof(struct f2fs_gc_kthread, _elname),	\
>  }
>  
> -#define F2FS_ATTR(name, mode, show, store) \
> -static struct f2fs_attr f2fs_attr_##name = __ATTR(name, mode, show, store)
> -
>  #define F2FS_RW_ATTR(name, elname)	\
>  	F2FS_ATTR_OFFSET(name, 0644, f2fs_sbi_show, f2fs_sbi_store, elname)
>  
>  F2FS_RW_ATTR(gc_min_sleep_time, min_sleep_time);
>  F2FS_RW_ATTR(gc_max_sleep_time, max_sleep_time);
>  F2FS_RW_ATTR(gc_no_gc_sleep_time, no_gc_sleep_time);
> +F2FS_ATTR_OFFSET(gc_long_idle, 0644, f2fs_sbi_show,
> +			 f2fs_gc_long_idle_store, long_idle);
> +F2FS_ATTR_OFFSET(gc_short_idle, 0644, f2fs_sbi_show,
> +			 f2fs_gc_short_idle_store, short_idle);
>  
>  #define ATTR_LIST(name) (&f2fs_attr_##name.attr)
>  static struct attribute *f2fs_attrs[] = {
>  	ATTR_LIST(gc_min_sleep_time),
>  	ATTR_LIST(gc_max_sleep_time),
>  	ATTR_LIST(gc_no_gc_sleep_time),
> +	ATTR_LIST(gc_long_idle),
> +	ATTR_LIST(gc_short_idle),
>  	NULL,
>  };
>  


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