Commit b1c57c1c authored by Jaegeuk Kim's avatar Jaegeuk Kim
Browse files

f2fs: add a sysfs entry to control max_victim_search 



Previously during SSR and GC, the maximum number of retrials to find a victim
segment was hard-coded by MAX_VICTIM_SEARCH, 4096 by default.

This number makes an effect on IO locality, when SSR mode is activated, which
results in performance fluctuation on some low-end devices.

If max_victim_search = 4, the victim will be searched like below.
("D" represents a dirty segment, and "*" indicates a selected victim segment.)

 D1 D2 D3 D4 D5 D6 D7 D8 D9
[   *       ]
      [   *    ]
            [         * ]
	                [ ....]

This patch adds a sysfs entry to control the number dynamically through:
  /sys/fs/f2fs/$dev/max_victim_search

Signed-off-by: default avatarJaegeuk Kim <jaegeuk.kim@samsung.com>
parent fb5566da

fs/f2fs/f2fs.h

+3 −0
Original line number Diff line number Diff line
@@ -451,6 +451,9 @@ struct f2fs_sb_info { 
	struct f2fs_gc_kthread	*gc_thread;	/* GC thread */

	unsigned int cur_victim_sec;		/* current victim section num */



	/* maximum # of trials to find a victim segment for SSR and GC */

	unsigned int max_victim_search;



	/*

	 * for stat information.

	 * one is for the LFS mode, and the other is for the SSR mode.

fs/f2fs/gc.c

+2 −2
Original line number Diff line number Diff line
@@ -163,8 +163,8 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type, 
		p->ofs_unit = sbi->segs_per_sec;

	}



	if (p->max_search > MAX_VICTIM_SEARCH)

		p->max_search = MAX_VICTIM_SEARCH;

	if (p->max_search > sbi->max_victim_search)

		p->max_search = sbi->max_victim_search;



	p->offset = sbi->last_victim[p->gc_mode];

}

fs/f2fs/gc.h

+1 −1
Original line number Diff line number Diff line
@@ -20,7 +20,7 @@ 
#define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */



/* Search max. number of dirty segments to select a victim segment */

#define MAX_VICTIM_SEARCH 4096 /* covers 8GB */

#define DEF_MAX_VICTIM_SEARCH 4096 /* covers 8GB */



struct f2fs_gc_kthread {

	struct task_struct *f2fs_gc_task;

fs/f2fs/super.c

+6 −0
Original line number Diff line number Diff line
@@ -74,6 +74,7 @@ static match_table_t f2fs_tokens = { 
enum {

	GC_THREAD,	/* struct f2fs_gc_thread */

	SM_INFO,	/* struct f2fs_sm_info */

	F2FS_SBI,	/* struct f2fs_sb_info */

};



struct f2fs_attr {
@@ -91,6 +92,8 @@ static unsigned char *__struct_ptr(struct f2fs_sb_info *sbi, int struct_type) 
		return (unsigned char *)sbi->gc_thread;

	else if (struct_type == SM_INFO)

		return (unsigned char *)SM_I(sbi);

	else if (struct_type == F2FS_SBI)

		return (unsigned char *)sbi;

	return NULL;

}
@@ -180,6 +183,7 @@ F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments); 
F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, max_small_discards, max_discards);

F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);

F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ipu_util, min_ipu_util);

F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, max_victim_search, max_victim_search);



#define ATTR_LIST(name) (&f2fs_attr_##name.attr)

static struct attribute *f2fs_attrs[] = {
@@ -191,6 +195,7 @@ static struct attribute *f2fs_attrs[] = { 
	ATTR_LIST(max_small_discards),

	ATTR_LIST(ipu_policy),

	ATTR_LIST(min_ipu_util),

	ATTR_LIST(max_victim_search),

	NULL,

};
@@ -775,6 +780,7 @@ static void init_sb_info(struct f2fs_sb_info *sbi) 
	sbi->node_ino_num = le32_to_cpu(raw_super->node_ino);

	sbi->meta_ino_num = le32_to_cpu(raw_super->meta_ino);

	sbi->cur_victim_sec = NULL_SECNO;

	sbi->max_victim_search = DEF_MAX_VICTIM_SEARCH;



	for (i = 0; i < NR_COUNT_TYPE; i++)

		atomic_set(&sbi->nr_pages[i], 0);

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