diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 7f730c4c8df2..834d0becae6d 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -22,7 +22,8 @@ Contact:	"Namjae Jeon" <namjae.jeon@samsung.com>
 Description:	Controls the victim selection policy for garbage collection.
 		Setting gc_idle = 0(default) will disable this option. Setting
 		gc_idle = 1 will select the Cost Benefit approach & setting
-		gc_idle = 2 will select the greedy approach.
+		gc_idle = 2 will select the greedy approach & setting
+		gc_idle = 3 will select the age-threshold based approach.
 
 What:		/sys/fs/f2fs/<disk>/reclaim_segments
 Date:		October 2013
diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
index 2b3aef2f5fa1..a2425c999586 100644
--- a/Documentation/filesystems/f2fs.rst
+++ b/Documentation/filesystems/f2fs.rst
@@ -266,6 +266,8 @@ inlinecrypt		 When possible, encrypt/decrypt the contents of encrypted
 			 inline encryption hardware. The on-disk format is
 			 unaffected. For more details, see
 			 Documentation/block/inline-encryption.rst.
+atgc			 Enable age-threshold garbage collection, it provides high
+			 effectiveness and efficiency on background GC.
 ======================== ============================================================
 
 Debugfs Entries
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 9e30ff6414b8..6059ce3758d8 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1620,7 +1620,7 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	f2fs_flush_sit_entries(sbi, cpc);
 
 	/* save inmem log status */
-	f2fs_save_inmem_curseg(sbi, CURSEG_COLD_DATA_PINNED);
+	f2fs_save_inmem_curseg(sbi);
 
 	err = do_checkpoint(sbi, cpc);
 	if (err)
@@ -1628,7 +1628,7 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	else
 		f2fs_clear_prefree_segments(sbi, cpc);
 
-	f2fs_restore_inmem_curseg(sbi, CURSEG_COLD_DATA_PINNED);
+	f2fs_restore_inmem_curseg(sbi);
 stop:
 	unblock_operations(sbi);
 	stat_inc_cp_count(sbi->stat_info);
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 011aea665ae4..6a20f2e664c4 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1416,7 +1416,7 @@ alloc:
 	set_summary(&sum, dn->nid, dn->ofs_in_node, ni.version);
 	old_blkaddr = dn->data_blkaddr;
 	f2fs_allocate_data_block(sbi, NULL, old_blkaddr, &dn->data_blkaddr,
-				&sum, seg_type, NULL, false);
+				&sum, seg_type, NULL);
 	if (GET_SEGNO(sbi, old_blkaddr) != NULL_SEGNO)
 		invalidate_mapping_pages(META_MAPPING(sbi),
 					old_blkaddr, old_blkaddr);
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 41a91aa8c262..cb679561f44d 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -397,6 +397,10 @@ static int stat_show(struct seq_file *s, void *v)
 			   si->curseg[CURSEG_COLD_DATA_PINNED],
 			   si->cursec[CURSEG_COLD_DATA_PINNED],
 			   si->curzone[CURSEG_COLD_DATA_PINNED]);
+		seq_printf(s, "  - ATGC   data: %8d %8d %8d\n",
+			   si->curseg[CURSEG_ALL_DATA_ATGC],
+			   si->cursec[CURSEG_ALL_DATA_ATGC],
+			   si->curzone[CURSEG_ALL_DATA_ATGC]);
 		seq_printf(s, "\n  - Valid: %d\n  - Dirty: %d\n",
 			   si->main_area_segs - si->dirty_count -
 			   si->prefree_count - si->free_segs,
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 7446ca639140..eedfea9503f8 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -98,6 +98,7 @@ extern const char *f2fs_fault_name[FAULT_MAX];
 #define F2FS_MOUNT_RESERVE_ROOT		0x01000000
 #define F2FS_MOUNT_DISABLE_CHECKPOINT	0x02000000
 #define F2FS_MOUNT_NORECOVERY		0x04000000
+#define F2FS_MOUNT_ATGC			0x08000000
 
 #define F2FS_OPTION(sbi)	((sbi)->mount_opt)
 #define clear_opt(sbi, option)	(F2FS_OPTION(sbi).opt &= ~F2FS_MOUNT_##option)
@@ -978,7 +979,7 @@ static inline void set_new_dnode(struct dnode_of_data *dn, struct inode *inode,
  */
 #define	NR_CURSEG_DATA_TYPE	(3)
 #define NR_CURSEG_NODE_TYPE	(3)
-#define NR_CURSEG_INMEM_TYPE	(1)
+#define NR_CURSEG_INMEM_TYPE	(2)
 #define NR_CURSEG_PERSIST_TYPE	(NR_CURSEG_DATA_TYPE + NR_CURSEG_NODE_TYPE)
 #define NR_CURSEG_TYPE		(NR_CURSEG_INMEM_TYPE + NR_CURSEG_PERSIST_TYPE)
 
@@ -992,6 +993,7 @@ enum {
 	NR_PERSISTENT_LOG,	/* number of persistent log */
 	CURSEG_COLD_DATA_PINNED = NR_PERSISTENT_LOG,
 				/* pinned file that needs consecutive block address */
+	CURSEG_ALL_DATA_ATGC,	/* SSR alloctor in hot/warm/cold data area */
 	NO_CHECK_TYPE,		/* number of persistent & inmem log */
 };
 
@@ -1238,6 +1240,18 @@ struct inode_management {
 	unsigned long ino_num;			/* number of entries */
 };
 
+/* for GC_AT */
+struct atgc_management {
+	bool atgc_enabled;			/* ATGC is enabled or not */
+	struct rb_root_cached root;		/* root of victim rb-tree */
+	struct list_head victim_list;		/* linked with all victim entries */
+	unsigned int victim_count;		/* victim count in rb-tree */
+	unsigned int candidate_ratio;		/* candidate ratio */
+	unsigned int max_candidate_count;	/* max candidate count */
+	unsigned int age_weight;		/* age weight, vblock_weight = 100 - age_weight */
+	unsigned long long age_threshold;	/* age threshold */
+};
+
 /* For s_flag in struct f2fs_sb_info */
 enum {
 	SBI_IS_DIRTY,				/* dirty flag for checkpoint */
@@ -1270,6 +1284,7 @@ enum {
 	GC_NORMAL,
 	GC_IDLE_CB,
 	GC_IDLE_GREEDY,
+	GC_IDLE_AT,
 	GC_URGENT_HIGH,
 	GC_URGENT_LOW,
 };
@@ -1521,6 +1536,7 @@ struct f2fs_sb_info {
 						 * race between GC and GC or CP
 						 */
 	struct f2fs_gc_kthread	*gc_thread;	/* GC thread */
+	struct atgc_management am;		/* atgc management */
 	unsigned int cur_victim_sec;		/* current victim section num */
 	unsigned int gc_mode;			/* current GC state */
 	unsigned int next_victim_seg[2];	/* next segment in victim section */
@@ -3338,8 +3354,11 @@ block_t f2fs_get_unusable_blocks(struct f2fs_sb_info *sbi);
 int f2fs_disable_cp_again(struct f2fs_sb_info *sbi, block_t unusable);
 void f2fs_release_discard_addrs(struct f2fs_sb_info *sbi);
 int f2fs_npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);
-void f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi, int type);
-void f2fs_restore_inmem_curseg(struct f2fs_sb_info *sbi, int type);
+void f2fs_init_inmem_curseg(struct f2fs_sb_info *sbi);
+void f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi);
+void f2fs_restore_inmem_curseg(struct f2fs_sb_info *sbi);
+void f2fs_get_new_segment(struct f2fs_sb_info *sbi,
+			unsigned int *newseg, bool new_sec, int dir);
 void f2fs_allocate_segment_for_resize(struct f2fs_sb_info *sbi, int type,
 					unsigned int start, unsigned int end);
 void f2fs_allocate_new_segment(struct f2fs_sb_info *sbi, int type);
@@ -3367,7 +3386,7 @@ void f2fs_replace_block(struct f2fs_sb_info *sbi, struct dnode_of_data *dn,
 void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
 			block_t old_blkaddr, block_t *new_blkaddr,
 			struct f2fs_summary *sum, int type,
-			struct f2fs_io_info *fio, bool from_gc);
+			struct f2fs_io_info *fio);
 void f2fs_wait_on_page_writeback(struct page *page,
 			enum page_type type, bool ordered, bool locked);
 void f2fs_wait_on_block_writeback(struct inode *inode, block_t blkaddr);
@@ -3506,6 +3525,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, bool background,
 			unsigned int segno);
 void f2fs_build_gc_manager(struct f2fs_sb_info *sbi);
 int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count);
+int __init f2fs_create_garbage_collection_cache(void);
+void f2fs_destroy_garbage_collection_cache(void);
 
 /*
  * recovery.c
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 697908c333e2..84b9dac942e3 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -21,6 +21,8 @@
 #include "gc.h"
 #include <trace/events/f2fs.h>
 
+static struct kmem_cache *victim_entry_slab;
+
 static unsigned int count_bits(const unsigned long *addr,
 				unsigned int offset, unsigned int len);
 
@@ -169,7 +171,16 @@ void f2fs_stop_gc_thread(struct f2fs_sb_info *sbi)
 
 static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
 {
-	int gc_mode = (gc_type == BG_GC) ? GC_CB : GC_GREEDY;
+	int gc_mode;
+
+	if (gc_type == BG_GC) {
+		if (sbi->am.atgc_enabled)
+			gc_mode = GC_AT;
+		else
+			gc_mode = GC_CB;
+	} else {
+		gc_mode = GC_GREEDY;
+	}
 
 	switch (sbi->gc_mode) {
 	case GC_IDLE_CB:
@@ -179,7 +190,11 @@ static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
 	case GC_URGENT_HIGH:
 		gc_mode = GC_GREEDY;
 		break;
+	case GC_IDLE_AT:
+		gc_mode = GC_AT;
+		break;
 	}
+
 	return gc_mode;
 }
 
@@ -193,6 +208,11 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
 		p->dirty_bitmap = dirty_i->dirty_segmap[type];
 		p->max_search = dirty_i->nr_dirty[type];
 		p->ofs_unit = 1;
+	} else if (p->alloc_mode == AT_SSR) {
+		p->gc_mode = GC_GREEDY;
+		p->dirty_bitmap = dirty_i->dirty_segmap[type];
+		p->max_search = dirty_i->nr_dirty[type];
+		p->ofs_unit = 1;
 	} else {
 		p->gc_mode = select_gc_type(sbi, gc_type);
 		p->ofs_unit = sbi->segs_per_sec;
@@ -212,6 +232,7 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
 	 */
 	if (gc_type != FG_GC &&
 			(sbi->gc_mode != GC_URGENT_HIGH) &&
+			(p->gc_mode != GC_AT && p->alloc_mode != AT_SSR) &&
 			p->max_search > sbi->max_victim_search)
 		p->max_search = sbi->max_victim_search;
 
@@ -229,10 +250,16 @@ static unsigned int get_max_cost(struct f2fs_sb_info *sbi,
 	/* SSR allocates in a segment unit */
 	if (p->alloc_mode == SSR)
 		return sbi->blocks_per_seg;
+	else if (p->alloc_mode == AT_SSR)
+		return UINT_MAX;
+
+	/* LFS */
 	if (p->gc_mode == GC_GREEDY)
 		return 2 * sbi->blocks_per_seg * p->ofs_unit;
 	else if (p->gc_mode == GC_CB)
 		return UINT_MAX;
+	else if (p->gc_mode == GC_AT)
+		return UINT_MAX;
 	else /* No other gc_mode */
 		return 0;
 }
@@ -298,8 +325,11 @@ static inline unsigned int get_gc_cost(struct f2fs_sb_info *sbi,
 	/* alloc_mode == LFS */
 	if (p->gc_mode == GC_GREEDY)
 		return get_valid_blocks(sbi, segno, true);
-	else
+	else if (p->gc_mode == GC_CB)
 		return get_cb_cost(sbi, segno);
+
+	f2fs_bug_on(sbi, 1);
+	return 0;
 }
 
 static unsigned int count_bits(const unsigned long *addr,
@@ -314,6 +344,273 @@ static unsigned int count_bits(const unsigned long *addr,
 	return sum;
 }
 
+static struct victim_entry *attach_victim_entry(struct f2fs_sb_info *sbi,
+				unsigned long long mtime, unsigned int segno,
+				struct rb_node *parent, struct rb_node **p,
+				bool left_most)
+{
+	struct atgc_management *am = &sbi->am;
+	struct victim_entry *ve;
+
+	ve =  f2fs_kmem_cache_alloc(victim_entry_slab, GFP_NOFS);
+
+	ve->mtime = mtime;
+	ve->segno = segno;
+
+	rb_link_node(&ve->rb_node, parent, p);
+	rb_insert_color_cached(&ve->rb_node, &am->root, left_most);
+
+	list_add_tail(&ve->list, &am->victim_list);
+
+	am->victim_count++;
+
+	return ve;
+}
+
+static void insert_victim_entry(struct f2fs_sb_info *sbi,
+				unsigned long long mtime, unsigned int segno)
+{
+	struct atgc_management *am = &sbi->am;
+	struct rb_node **p;
+	struct rb_node *parent = NULL;
+	bool left_most = true;
+
+	p = f2fs_lookup_rb_tree_ext(sbi, &am->root, &parent, mtime, &left_most);
+	attach_victim_entry(sbi, mtime, segno, parent, p, left_most);
+}
+
+static void add_victim_entry(struct f2fs_sb_info *sbi,
+				struct victim_sel_policy *p, unsigned int segno)
+{
+	struct sit_info *sit_i = SIT_I(sbi);
+	unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
+	unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
+	unsigned long long mtime = 0;
+	unsigned int i;
+
+	if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
+		if (p->gc_mode == GC_AT &&
+			get_valid_blocks(sbi, segno, true) == 0)
+			return;
+
+		if (p->alloc_mode == AT_SSR &&
+			get_seg_entry(sbi, segno)->ckpt_valid_blocks == 0)
+			return;
+	}
+
+	for (i = 0; i < sbi->segs_per_sec; i++)
+		mtime += get_seg_entry(sbi, start + i)->mtime;
+	mtime = div_u64(mtime, sbi->segs_per_sec);
+
+	/* Handle if the system time has changed by the user */
+	if (mtime < sit_i->min_mtime)
+		sit_i->min_mtime = mtime;
+	if (mtime > sit_i->max_mtime)
+		sit_i->max_mtime = mtime;
+	if (mtime < sit_i->dirty_min_mtime)
+		sit_i->dirty_min_mtime = mtime;
+	if (mtime > sit_i->dirty_max_mtime)
+		sit_i->dirty_max_mtime = mtime;
+
+	/* don't choose young section as candidate */
+	if (sit_i->dirty_max_mtime - mtime < p->age_threshold)
+		return;
+
+	insert_victim_entry(sbi, mtime, segno);
+}
+
+static struct rb_node *lookup_central_victim(struct f2fs_sb_info *sbi,
+						struct victim_sel_policy *p)
+{
+	struct atgc_management *am = &sbi->am;
+	struct rb_node *parent = NULL;
+	bool left_most;
+
+	f2fs_lookup_rb_tree_ext(sbi, &am->root, &parent, p->age, &left_most);
+
+	return parent;
+}
+
+static void atgc_lookup_victim(struct f2fs_sb_info *sbi,
+						struct victim_sel_policy *p)
+{
+	struct sit_info *sit_i = SIT_I(sbi);
+	struct atgc_management *am = &sbi->am;
+	struct rb_root_cached *root = &am->root;
+	struct rb_node *node;
+	struct rb_entry *re;
+	struct victim_entry *ve;
+	unsigned long long total_time;
+	unsigned long long age, u, accu;
+	unsigned long long max_mtime = sit_i->dirty_max_mtime;
+	unsigned long long min_mtime = sit_i->dirty_min_mtime;
+	unsigned int sec_blocks = BLKS_PER_SEC(sbi);
+	unsigned int vblocks;
+	unsigned int dirty_threshold = max(am->max_candidate_count,
+					am->candidate_ratio *
+					am->victim_count / 100);
+	unsigned int age_weight = am->age_weight;
+	unsigned int cost;
+	unsigned int iter = 0;
+
+	if (max_mtime < min_mtime)
+		return;
+
+	max_mtime += 1;
+	total_time = max_mtime - min_mtime;
+
+	accu = div64_u64(ULLONG_MAX, total_time);
+	accu = min_t(unsigned long long, div_u64(accu, 100),
+					DEFAULT_ACCURACY_CLASS);
+
+	node = rb_first_cached(root);
+next:
+	re = rb_entry_safe(node, struct rb_entry, rb_node);
+	if (!re)
+		return;
+
+	ve = (struct victim_entry *)re;
+
+	if (ve->mtime >= max_mtime || ve->mtime < min_mtime)
+		goto skip;
+
+	/* age = 10000 * x% * 60 */
+	age = div64_u64(accu * (max_mtime - ve->mtime), total_time) *
+								age_weight;
+
+	vblocks = get_valid_blocks(sbi, ve->segno, true);
+	f2fs_bug_on(sbi, !vblocks || vblocks == sec_blocks);
+
+	/* u = 10000 * x% * 40 */
+	u = div64_u64(accu * (sec_blocks - vblocks), sec_blocks) *
+							(100 - age_weight);
+
+	f2fs_bug_on(sbi, age + u >= UINT_MAX);
+
+	cost = UINT_MAX - (age + u);
+	iter++;
+
+	if (cost < p->min_cost ||
+			(cost == p->min_cost && age > p->oldest_age)) {
+		p->min_cost = cost;
+		p->oldest_age = age;
+		p->min_segno = ve->segno;
+	}
+skip:
+	if (iter < dirty_threshold) {
+		node = rb_next(node);
+		goto next;
+	}
+}
+
+/*
+ * select candidates around source section in range of
+ * [target - dirty_threshold, target + dirty_threshold]
+ */
+static void atssr_lookup_victim(struct f2fs_sb_info *sbi,
+						struct victim_sel_policy *p)
+{
+	struct sit_info *sit_i = SIT_I(sbi);
+	struct atgc_management *am = &sbi->am;
+	struct rb_node *node;
+	struct rb_entry *re;
+	struct victim_entry *ve;
+	unsigned long long age;
+	unsigned long long max_mtime = sit_i->dirty_max_mtime;
+	unsigned long long min_mtime = sit_i->dirty_min_mtime;
+	unsigned int seg_blocks = sbi->blocks_per_seg;
+	unsigned int vblocks;
+	unsigned int dirty_threshold = max(am->max_candidate_count,
+					am->candidate_ratio *
+					am->victim_count / 100);
+	unsigned int cost;
+	unsigned int iter = 0;
+	int stage = 0;
+
+	if (max_mtime < min_mtime)
+		return;
+	max_mtime += 1;
+next_stage:
+	node = lookup_central_victim(sbi, p);
+next_node:
+	re = rb_entry_safe(node, struct rb_entry, rb_node);
+	if (!re) {
+		if (stage == 0)
+			goto skip_stage;
+		return;
+	}
+
+	ve = (struct victim_entry *)re;
+
+	if (ve->mtime >= max_mtime || ve->mtime < min_mtime)
+		goto skip_node;
+
+	age = max_mtime - ve->mtime;
+
+	vblocks = get_seg_entry(sbi, ve->segno)->ckpt_valid_blocks;
+	f2fs_bug_on(sbi, !vblocks);
+
+	/* rare case */
+	if (vblocks == seg_blocks)
+		goto skip_node;
+
+	iter++;
+
+	age = max_mtime - abs(p->age - age);
+	cost = UINT_MAX - vblocks;
+
+	if (cost < p->min_cost ||
+			(cost == p->min_cost && age > p->oldest_age)) {
+		p->min_cost = cost;
+		p->oldest_age = age;
+		p->min_segno = ve->segno;
+	}
+skip_node:
+	if (iter < dirty_threshold) {
+		if (stage == 0)
+			node = rb_prev(node);
+		else if (stage == 1)
+			node = rb_next(node);
+		goto next_node;
+	}
+skip_stage:
+	if (stage < 1) {
+		stage++;
+		iter = 0;
+		goto next_stage;
+	}
+}
+static void lookup_victim_by_age(struct f2fs_sb_info *sbi,
+						struct victim_sel_policy *p)
+{
+	f2fs_bug_on(sbi, !f2fs_check_rb_tree_consistence(sbi,
+						&sbi->am.root, true));
+
+	if (p->gc_mode == GC_AT)
+		atgc_lookup_victim(sbi, p);
+	else if (p->alloc_mode == AT_SSR)
+		atssr_lookup_victim(sbi, p);
+	else
+		f2fs_bug_on(sbi, 1);
+}
+
+static void release_victim_entry(struct f2fs_sb_info *sbi)
+{
+	struct atgc_management *am = &sbi->am;
+	struct victim_entry *ve, *tmp;
+
+	list_for_each_entry_safe(ve, tmp, &am->victim_list, list) {
+		list_del(&ve->list);
+		kmem_cache_free(victim_entry_slab, ve);
+		am->victim_count--;
+	}
+
+	am->root = RB_ROOT_CACHED;
+
+	f2fs_bug_on(sbi, am->victim_count);
+	f2fs_bug_on(sbi, !list_empty(&am->victim_list));
+}
+
 /*
  * This function is called from two paths.
  * One is garbage collection and the other is SSR segment selection.
@@ -323,25 +620,37 @@ static unsigned int count_bits(const unsigned long *addr,
  * which has minimum valid blocks and removes it from dirty seglist.
  */
 static int get_victim_by_default(struct f2fs_sb_info *sbi,
-		unsigned int *result, int gc_type, int type, char alloc_mode)
+			unsigned int *result, int gc_type, int type,
+			char alloc_mode, unsigned long long age)
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
 	struct sit_info *sm = SIT_I(sbi);
 	struct victim_sel_policy p;
 	unsigned int secno, last_victim;
 	unsigned int last_segment;
-	unsigned int nsearched = 0;
+	unsigned int nsearched;
+	bool is_atgc;
 	int ret = 0;
 
 	mutex_lock(&dirty_i->seglist_lock);
 	last_segment = MAIN_SECS(sbi) * sbi->segs_per_sec;
 
 	p.alloc_mode = alloc_mode;
-	select_policy(sbi, gc_type, type, &p);
+	p.age = age;
+	p.age_threshold = sbi->am.age_threshold;
 
+retry:
+	select_policy(sbi, gc_type, type, &p);
 	p.min_segno = NULL_SEGNO;
+	p.oldest_age = 0;
 	p.min_cost = get_max_cost(sbi, &p);
 
+	is_atgc = (p.gc_mode == GC_AT || p.alloc_mode == AT_SSR);
+	nsearched = 0;
+
+	if (is_atgc)
+		SIT_I(sbi)->dirty_min_mtime = ULLONG_MAX;
+
 	if (*result != NULL_SEGNO) {
 		if (!get_valid_blocks(sbi, *result, false)) {
 			ret = -ENODATA;
@@ -422,11 +731,16 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
 		/* Don't touch checkpointed data */
 		if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED) &&
 					get_ckpt_valid_blocks(sbi, segno) &&
-					p.alloc_mode != SSR))
+					p.alloc_mode == LFS))
 			goto next;
 		if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
 			goto next;
 
+		if (is_atgc) {
+			add_victim_entry(sbi, &p, segno);
+			goto next;
+		}
+
 		cost = get_gc_cost(sbi, segno, &p);
 
 		if (p.min_cost > cost) {
@@ -445,6 +759,19 @@ next:
 			break;
 		}
 	}
+
+	/* get victim for GC_AT/AT_SSR */
+	if (is_atgc) {
+		lookup_victim_by_age(sbi, &p);
+		release_victim_entry(sbi);
+	}
+
+	if (is_atgc && p.min_segno == NULL_SEGNO &&
+			sm->elapsed_time < p.age_threshold) {
+		p.age_threshold = 0;
+		goto retry;
+	}
+
 	if (p.min_segno != NULL_SEGNO) {
 got_it:
 		*result = (p.min_segno / p.ofs_unit) * p.ofs_unit;
@@ -793,6 +1120,8 @@ static int move_data_block(struct inode *inode, block_t bidx,
 	block_t newaddr;
 	int err = 0;
 	bool lfs_mode = f2fs_lfs_mode(fio.sbi);
+	int type = fio.sbi->am.atgc_enabled ?
+				CURSEG_ALL_DATA_ATGC : CURSEG_COLD_DATA;
 
 	/* do not read out */
 	page = f2fs_grab_cache_page(inode->i_mapping, bidx, false);
@@ -879,7 +1208,7 @@ static int move_data_block(struct inode *inode, block_t bidx,
 	}
 
 	f2fs_allocate_data_block(fio.sbi, NULL, fio.old_blkaddr, &newaddr,
-				&sum, CURSEG_COLD_DATA, NULL, true);
+				&sum, type, NULL);
 
 	fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(fio.sbi),
 				newaddr, FGP_LOCK | FGP_CREAT, GFP_NOFS);
@@ -1185,7 +1514,7 @@ static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim,
 
 	down_write(&sit_i->sentry_lock);
 	ret = DIRTY_I(sbi)->v_ops->get_victim(sbi, victim, gc_type,
-					      NO_CHECK_TYPE, LFS);
+					      NO_CHECK_TYPE, LFS, 0);
 	up_write(&sit_i->sentry_lock);
 	return ret;
 }
@@ -1216,6 +1545,8 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 		end_segno -= sbi->segs_per_sec -
 					f2fs_usable_segs_in_sec(sbi, segno);
 
+	sanity_check_seg_type(sbi, get_seg_entry(sbi, segno)->type);
+
 	/* readahead multi ssa blocks those have contiguous address */
 	if (__is_large_section(sbi))
 		f2fs_ra_meta_pages(sbi, GET_SUM_BLOCK(sbi, segno),
@@ -1426,6 +1757,37 @@ stop:
 	return ret;
 }
 
+int __init f2fs_create_garbage_collection_cache(void)
+{
+	victim_entry_slab = f2fs_kmem_cache_create("f2fs_victim_entry",
+					sizeof(struct victim_entry));
+	if (!victim_entry_slab)
+		return -ENOMEM;
+	return 0;
+}
+
+void f2fs_destroy_garbage_collection_cache(void)
+{
+	kmem_cache_destroy(victim_entry_slab);
+}
+
+static void init_atgc_management(struct f2fs_sb_info *sbi)
+{
+	struct atgc_management *am = &sbi->am;
+
+	if (test_opt(sbi, ATGC) &&
+		SIT_I(sbi)->elapsed_time >= DEF_GC_THREAD_AGE_THRESHOLD)
+		am->atgc_enabled = true;
+
+	am->root = RB_ROOT_CACHED;
+	INIT_LIST_HEAD(&am->victim_list);
+	am->victim_count = 0;
+
+	am->candidate_ratio = DEF_GC_THREAD_CANDIDATE_RATIO;
+	am->max_candidate_count = DEF_GC_THREAD_MAX_CANDIDATE_COUNT;
+	am->age_weight = DEF_GC_THREAD_AGE_WEIGHT;
+}
+
 void f2fs_build_gc_manager(struct f2fs_sb_info *sbi)
 {
 	DIRTY_I(sbi)->v_ops = &default_v_ops;
@@ -1436,6 +1798,8 @@ void f2fs_build_gc_manager(struct f2fs_sb_info *sbi)
 	if (f2fs_is_multi_device(sbi) && !__is_large_section(sbi))
 		SIT_I(sbi)->last_victim[ALLOC_NEXT] =
 				GET_SEGNO(sbi, FDEV(0).end_blk) + 1;
+
+	init_atgc_management(sbi);
 }
 
 static int free_segment_range(struct f2fs_sb_info *sbi,
diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index ee5d7f30a1f8..0c8dae12dc51 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -14,6 +14,14 @@
 #define DEF_GC_THREAD_MIN_SLEEP_TIME	30000	/* milliseconds */
 #define DEF_GC_THREAD_MAX_SLEEP_TIME	60000
 #define DEF_GC_THREAD_NOGC_SLEEP_TIME	300000	/* wait 5 min */
+
+/* choose candidates from sections which has age of more than 7 days */
+#define DEF_GC_THREAD_AGE_THRESHOLD		(60 * 60 * 24 * 7)
+#define DEF_GC_THREAD_CANDIDATE_RATIO		20	/* select 20% oldest sections as candidates */
+#define DEF_GC_THREAD_MAX_CANDIDATE_COUNT	10	/* select at most 10 sections as candidates */
+#define DEF_GC_THREAD_AGE_WEIGHT		60	/* age weight */
+#define DEFAULT_ACCURACY_CLASS			10000	/* accuracy class */
+
 #define LIMIT_INVALID_BLOCK	40 /* percentage over total user space */
 #define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */
 
@@ -41,6 +49,23 @@ struct gc_inode_list {
 	struct radix_tree_root iroot;
 };
 
+struct victim_info {
+	unsigned long long mtime;	/* mtime of section */
+	unsigned int segno;		/* section No. */
+};
+
+struct victim_entry {
+	struct rb_node rb_node;		/* rb node located in rb-tree */
+	union {
+		struct {
+			unsigned long long mtime;	/* mtime of section */
+			unsigned int segno;		/* segment No. */
+		};
+		struct victim_info vi;	/* victim info */
+	};
+	struct list_head list;
+};
+
 /*
  * inline functions
  */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 8aa36aa25177..6335523090e9 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2424,9 +2424,9 @@ static void write_current_sum_page(struct f2fs_sb_info *sbi,
 	f2fs_put_page(page, 1);
 }
 
-static int is_next_segment_free(struct f2fs_sb_info *sbi, int type)
+static int is_next_segment_free(struct f2fs_sb_info *sbi,
+				struct curseg_info *curseg, int type)
 {
-	struct curseg_info *curseg = CURSEG_I(sbi, type);
 	unsigned int segno = curseg->segno + 1;
 	struct free_segmap_info *free_i = FREE_I(sbi);
 
@@ -2530,6 +2530,7 @@ static void reset_curseg(struct f2fs_sb_info *sbi, int type, int modified)
 {
 	struct curseg_info *curseg = CURSEG_I(sbi, type);
 	struct summary_footer *sum_footer;
+	unsigned short seg_type = curseg->seg_type;
 
 	curseg->inited = true;
 	curseg->segno = curseg->next_segno;
@@ -2539,16 +2540,22 @@ static void reset_curseg(struct f2fs_sb_info *sbi, int type, int modified)
 
 	sum_footer = &(curseg->sum_blk->footer);
 	memset(sum_footer, 0, sizeof(struct summary_footer));
-	if (IS_DATASEG(curseg->seg_type))
+
+	sanity_check_seg_type(sbi, seg_type);
+
+	if (IS_DATASEG(seg_type))
 		SET_SUM_TYPE(sum_footer, SUM_TYPE_DATA);
-	if (IS_NODESEG(curseg->seg_type))
+	if (IS_NODESEG(seg_type))
 		SET_SUM_TYPE(sum_footer, SUM_TYPE_NODE);
-	__set_sit_entry_type(sbi, curseg->seg_type, curseg->segno, modified);
+	__set_sit_entry_type(sbi, seg_type, curseg->segno, modified);
 }
 
 static unsigned int __get_next_segno(struct f2fs_sb_info *sbi, int type)
 {
 	struct curseg_info *curseg = CURSEG_I(sbi, type);
+	unsigned short seg_type = curseg->seg_type;
+
+	sanity_check_seg_type(sbi, seg_type);
 
 	/* if segs_per_sec is large than 1, we need to keep original policy. */
 	if (__is_large_section(sbi))
@@ -2562,8 +2569,7 @@ static unsigned int __get_next_segno(struct f2fs_sb_info *sbi, int type)
 		return 0;
 
 	if (test_opt(sbi, NOHEAP) &&
-		(curseg->seg_type == CURSEG_HOT_DATA ||
-		IS_NODESEG(curseg->seg_type)))
+		(seg_type == CURSEG_HOT_DATA || IS_NODESEG(seg_type)))
 		return 0;
 
 	if (SIT_I(sbi)->last_victim[ALLOC_NEXT])
@@ -2639,7 +2645,7 @@ static void __refresh_next_blkoff(struct f2fs_sb_info *sbi,
  * This function always allocates a used segment(from dirty seglist) by SSR
  * manner, so it should recover the existing segment information of valid blocks
  */
-static void change_curseg(struct f2fs_sb_info *sbi, int type)
+static void change_curseg(struct f2fs_sb_info *sbi, int type, bool flush)
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
 	struct curseg_info *curseg = CURSEG_I(sbi, type);
@@ -2647,8 +2653,10 @@ static void change_curseg(struct f2fs_sb_info *sbi, int type)
 	struct f2fs_summary_block *sum_node;
 	struct page *sum_page;
 
-	write_sum_page(sbi, curseg->sum_blk,
-				GET_SUM_BLOCK(sbi, curseg->segno));
+	if (flush)
+		write_sum_page(sbi, curseg->sum_blk,
+					GET_SUM_BLOCK(sbi, curseg->segno));
+
 	__set_test_and_inuse(sbi, new_segno);
 
 	mutex_lock(&dirty_i->seglist_lock);
@@ -2667,7 +2675,56 @@ static void change_curseg(struct f2fs_sb_info *sbi, int type)
 	f2fs_put_page(sum_page, 1);
 }
 
-void f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi, int type)
+static int get_ssr_segment(struct f2fs_sb_info *sbi, int type,
+				int alloc_mode, unsigned long long age);
+
+static void get_atssr_segment(struct f2fs_sb_info *sbi, int type,
+					int target_type, int alloc_mode,
+					unsigned long long age)
+{
+	struct curseg_info *curseg = CURSEG_I(sbi, type);
+
+	curseg->seg_type = target_type;
+
+	if (get_ssr_segment(sbi, type, alloc_mode, age)) {
+		struct seg_entry *se = get_seg_entry(sbi, curseg->next_segno);
+
+		curseg->seg_type = se->type;
+		change_curseg(sbi, type, true);
+	} else {
+		/* allocate cold segment by default */
+		curseg->seg_type = CURSEG_COLD_DATA;
+		new_curseg(sbi, type, true);
+	}
+	stat_inc_seg_type(sbi, curseg);
+}
+
+static void __f2fs_init_atgc_curseg(struct f2fs_sb_info *sbi)
+{
+	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_ALL_DATA_ATGC);
+
+	if (!sbi->am.atgc_enabled)
+		return;
+
+	down_read(&SM_I(sbi)->curseg_lock);
+
+	mutex_lock(&curseg->curseg_mutex);
+	down_write(&SIT_I(sbi)->sentry_lock);
+
+	get_atssr_segment(sbi, CURSEG_ALL_DATA_ATGC, CURSEG_COLD_DATA, SSR, 0);
+
+	up_write(&SIT_I(sbi)->sentry_lock);
+	mutex_unlock(&curseg->curseg_mutex);
+
+	up_read(&SM_I(sbi)->curseg_lock);
+
+}
+void f2fs_init_inmem_curseg(struct f2fs_sb_info *sbi)
+{
+	__f2fs_init_atgc_curseg(sbi);
+}
+
+static void __f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi, int type)
 {
 	struct curseg_info *curseg = CURSEG_I(sbi, type);
 
@@ -2687,7 +2744,15 @@ out:
 	mutex_unlock(&curseg->curseg_mutex);
 }
 
-void f2fs_restore_inmem_curseg(struct f2fs_sb_info *sbi, int type)
+void f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi)
+{
+	__f2fs_save_inmem_curseg(sbi, CURSEG_COLD_DATA_PINNED);
+
+	if (sbi->am.atgc_enabled)
+		__f2fs_save_inmem_curseg(sbi, CURSEG_ALL_DATA_ATGC);
+}
+
+static void __f2fs_restore_inmem_curseg(struct f2fs_sb_info *sbi, int type)
 {
 	struct curseg_info *curseg = CURSEG_I(sbi, type);
 
@@ -2704,23 +2769,35 @@ out:
 	mutex_unlock(&curseg->curseg_mutex);
 }
 
-static int get_ssr_segment(struct f2fs_sb_info *sbi, int type)
+void f2fs_restore_inmem_curseg(struct f2fs_sb_info *sbi)
+{
+	__f2fs_restore_inmem_curseg(sbi, CURSEG_COLD_DATA_PINNED);
+
+	if (sbi->am.atgc_enabled)
+		__f2fs_restore_inmem_curseg(sbi, CURSEG_ALL_DATA_ATGC);
+}
+
+static int get_ssr_segment(struct f2fs_sb_info *sbi, int type,
+				int alloc_mode, unsigned long long age)
 {
 	struct curseg_info *curseg = CURSEG_I(sbi, type);
 	const struct victim_selection *v_ops = DIRTY_I(sbi)->v_ops;
 	unsigned segno = NULL_SEGNO;
+	unsigned short seg_type = curseg->seg_type;
 	int i, cnt;
 	bool reversed = false;
 
+	sanity_check_seg_type(sbi, seg_type);
+
 	/* f2fs_need_SSR() already forces to do this */
-	if (!v_ops->get_victim(sbi, &segno, BG_GC, type, SSR)) {
+	if (!v_ops->get_victim(sbi, &segno, BG_GC, seg_type, alloc_mode, age)) {
 		curseg->next_segno = segno;
 		return 1;
 	}
 
 	/* For node segments, let's do SSR more intensively */
-	if (IS_NODESEG(type)) {
-		if (type >= CURSEG_WARM_NODE) {
+	if (IS_NODESEG(seg_type)) {
+		if (seg_type >= CURSEG_WARM_NODE) {
 			reversed = true;
 			i = CURSEG_COLD_NODE;
 		} else {
@@ -2728,7 +2805,7 @@ static int get_ssr_segment(struct f2fs_sb_info *sbi, int type)
 		}
 		cnt = NR_CURSEG_NODE_TYPE;
 	} else {
-		if (type >= CURSEG_WARM_DATA) {
+		if (seg_type >= CURSEG_WARM_DATA) {
 			reversed = true;
 			i = CURSEG_COLD_DATA;
 		} else {
@@ -2738,9 +2815,9 @@ static int get_ssr_segment(struct f2fs_sb_info *sbi, int type)
 	}
 
 	for (; cnt-- > 0; reversed ? i-- : i++) {
-		if (i == type)
+		if (i == seg_type)
 			continue;
-		if (!v_ops->get_victim(sbi, &segno, BG_GC, i, SSR)) {
+		if (!v_ops->get_victim(sbi, &segno, BG_GC, i, alloc_mode, age)) {
 			curseg->next_segno = segno;
 			return 1;
 		}
@@ -2769,13 +2846,15 @@ static void allocate_segment_by_default(struct f2fs_sb_info *sbi,
 	if (force)
 		new_curseg(sbi, type, true);
 	else if (!is_set_ckpt_flags(sbi, CP_CRC_RECOVERY_FLAG) &&
-					type == CURSEG_WARM_NODE)
+					curseg->seg_type == CURSEG_WARM_NODE)
 		new_curseg(sbi, type, false);
-	else if (curseg->alloc_type == LFS && is_next_segment_free(sbi, type) &&
+	else if (curseg->alloc_type == LFS &&
+			is_next_segment_free(sbi, curseg, type) &&
 			likely(!is_sbi_flag_set(sbi, SBI_CP_DISABLED)))
 		new_curseg(sbi, type, false);
-	else if (f2fs_need_SSR(sbi) && get_ssr_segment(sbi, type))
-		change_curseg(sbi, type);
+	else if (f2fs_need_SSR(sbi) &&
+			get_ssr_segment(sbi, type, SSR, 0))
+		change_curseg(sbi, type, true);
 	else
 		new_curseg(sbi, type, false);
 
@@ -2796,8 +2875,8 @@ void f2fs_allocate_segment_for_resize(struct f2fs_sb_info *sbi, int type,
 	if (segno < start || segno > end)
 		goto unlock;
 
-	if (f2fs_need_SSR(sbi) && get_ssr_segment(sbi, type))
-		change_curseg(sbi, type);
+	if (f2fs_need_SSR(sbi) && get_ssr_segment(sbi, type, SSR, 0))
+		change_curseg(sbi, type, true);
 	else
 		new_curseg(sbi, type, true);
 
@@ -3016,10 +3095,9 @@ out:
 	return err;
 }
 
-static bool __has_curseg_space(struct f2fs_sb_info *sbi, int type)
+static bool __has_curseg_space(struct f2fs_sb_info *sbi,
+					struct curseg_info *curseg)
 {
-	struct curseg_info *curseg = CURSEG_I(sbi, type);
-
 	return curseg->next_blkoff < f2fs_usable_blks_in_seg(sbi,
 							curseg->segno);
 }
@@ -3161,8 +3239,13 @@ static int __get_segment_type_6(struct f2fs_io_info *fio)
 	if (fio->type == DATA) {
 		struct inode *inode = fio->page->mapping->host;
 
-		if (is_cold_data(fio->page) || file_is_cold(inode) ||
-				f2fs_compressed_file(inode))
+		if (is_cold_data(fio->page)) {
+			if (fio->sbi->am.atgc_enabled)
+				return CURSEG_ALL_DATA_ATGC;
+			else
+				return CURSEG_COLD_DATA;
+		}
+		if (file_is_cold(inode) || f2fs_compressed_file(inode))
 			return CURSEG_COLD_DATA;
 		if (file_is_hot(inode) ||
 				is_inode_flag_set(inode, FI_HOT_DATA) ||
@@ -3208,19 +3291,29 @@ static int __get_segment_type(struct f2fs_io_info *fio)
 void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
 		block_t old_blkaddr, block_t *new_blkaddr,
 		struct f2fs_summary *sum, int type,
-		struct f2fs_io_info *fio, bool from_gc)
+		struct f2fs_io_info *fio)
 {
 	struct sit_info *sit_i = SIT_I(sbi);
 	struct curseg_info *curseg = CURSEG_I(sbi, type);
 	unsigned long long old_mtime;
+	bool from_gc = (type == CURSEG_ALL_DATA_ATGC);
+	struct seg_entry *se = NULL;
 
 	down_read(&SM_I(sbi)->curseg_lock);
 
 	mutex_lock(&curseg->curseg_mutex);
 	down_write(&sit_i->sentry_lock);
 
+	if (from_gc) {
+		f2fs_bug_on(sbi, GET_SEGNO(sbi, old_blkaddr) == NULL_SEGNO);
+		se = get_seg_entry(sbi, GET_SEGNO(sbi, old_blkaddr));
+		sanity_check_seg_type(sbi, se->type);
+		f2fs_bug_on(sbi, IS_NODESEG(se->type));
+	}
 	*new_blkaddr = NEXT_FREE_BLKADDR(sbi, curseg);
 
+	f2fs_bug_on(sbi, curseg->next_blkoff >= sbi->blocks_per_seg);
+
 	f2fs_wait_discard_bio(sbi, *new_blkaddr);
 
 	/*
@@ -3250,9 +3343,13 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
 	if (GET_SEGNO(sbi, old_blkaddr) != NULL_SEGNO)
 		update_sit_entry(sbi, old_blkaddr, -1);
 
-	if (!__has_curseg_space(sbi, type))
-		sit_i->s_ops->allocate_segment(sbi, type, false);
-
+	if (!__has_curseg_space(sbi, curseg)) {
+		if (from_gc)
+			get_atssr_segment(sbi, type, se->type,
+						AT_SSR, se->mtime);
+		else
+			sit_i->s_ops->allocate_segment(sbi, type, false);
+	}
 	/*
 	 * segment dirty status should be updated after segment allocation,
 	 * so we just need to update status only one time after previous
@@ -3318,8 +3415,7 @@ static void do_write_page(struct f2fs_summary *sum, struct f2fs_io_info *fio)
 		down_read(&fio->sbi->io_order_lock);
 reallocate:
 	f2fs_allocate_data_block(fio->sbi, fio->page, fio->old_blkaddr,
-			&fio->new_blkaddr, sum, type, fio,
-			is_cold_data(fio->page));
+			&fio->new_blkaddr, sum, type, fio);
 	if (GET_SEGNO(fio->sbi, fio->old_blkaddr) != NULL_SEGNO)
 		invalidate_mapping_pages(META_MAPPING(fio->sbi),
 					fio->old_blkaddr, fio->old_blkaddr);
@@ -3481,7 +3577,7 @@ void f2fs_do_replace_block(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 	/* change the current segment */
 	if (segno != curseg->segno) {
 		curseg->next_segno = segno;
-		change_curseg(sbi, type);
+		change_curseg(sbi, type, true);
 	}
 
 	curseg->next_blkoff = GET_BLKOFF_FROM_SEG0(sbi, new_blkaddr);
@@ -3508,7 +3604,7 @@ void f2fs_do_replace_block(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 	if (recover_curseg) {
 		if (old_cursegno != curseg->segno) {
 			curseg->next_segno = old_cursegno;
-			change_curseg(sbi, type);
+			change_curseg(sbi, type, true);
 		}
 		curseg->next_blkoff = old_blkoff;
 	}
@@ -4263,6 +4359,8 @@ static int build_curseg(struct f2fs_sb_info *sbi)
 			array[i].seg_type = CURSEG_HOT_DATA + i;
 		else if (i == CURSEG_COLD_DATA_PINNED)
 			array[i].seg_type = CURSEG_COLD_DATA;
+		else if (i == CURSEG_ALL_DATA_ATGC)
+			array[i].seg_type = CURSEG_COLD_DATA;
 		array[i].segno = NULL_SEGNO;
 		array[i].next_blkoff = 0;
 		array[i].inited = false;
@@ -4509,6 +4607,8 @@ static int sanity_check_curseg(struct f2fs_sb_info *sbi)
 		struct seg_entry *se = get_seg_entry(sbi, curseg->segno);
 		unsigned int blkofs = curseg->next_blkoff;
 
+		sanity_check_seg_type(sbi, curseg->seg_type);
+
 		if (f2fs_test_bit(blkofs, se->cur_valid_map))
 			goto out;
 
@@ -4935,6 +5035,7 @@ static void init_min_max_mtime(struct f2fs_sb_info *sbi)
 			sit_i->min_mtime = mtime;
 	}
 	sit_i->max_mtime = get_mtime(sbi, false);
+	sit_i->dirty_max_mtime = 0;
 	up_write(&sit_i->sentry_lock);
 }
 
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index ddaffe30f992..47b888ad913b 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -24,6 +24,12 @@
 #define IS_DATASEG(t)	((t) <= CURSEG_COLD_DATA)
 #define IS_NODESEG(t)	((t) >= CURSEG_HOT_NODE && (t) <= CURSEG_COLD_NODE)
 
+static inline void sanity_check_seg_type(struct f2fs_sb_info *sbi,
+						unsigned short seg_type)
+{
+	f2fs_bug_on(sbi, seg_type >= NR_PERSISTENT_LOG);
+}
+
 #define IS_HOT(t)	((t) == CURSEG_HOT_NODE || (t) == CURSEG_HOT_DATA)
 #define IS_WARM(t)	((t) == CURSEG_WARM_NODE || (t) == CURSEG_WARM_DATA)
 #define IS_COLD(t)	((t) == CURSEG_COLD_NODE || (t) == CURSEG_COLD_DATA)
@@ -35,7 +41,8 @@
 	 ((seg) == CURSEG_I(sbi, CURSEG_HOT_NODE)->segno) ||	\
 	 ((seg) == CURSEG_I(sbi, CURSEG_WARM_NODE)->segno) ||	\
 	 ((seg) == CURSEG_I(sbi, CURSEG_COLD_NODE)->segno) ||	\
-	 ((seg) == CURSEG_I(sbi, CURSEG_COLD_DATA_PINNED)->segno))
+	 ((seg) == CURSEG_I(sbi, CURSEG_COLD_DATA_PINNED)->segno) ||	\
+	 ((seg) == CURSEG_I(sbi, CURSEG_ALL_DATA_ATGC)->segno))
 
 #define IS_CURSEC(sbi, secno)						\
 	(((secno) == CURSEG_I(sbi, CURSEG_HOT_DATA)->segno /		\
@@ -51,6 +58,8 @@
 	 ((secno) == CURSEG_I(sbi, CURSEG_COLD_NODE)->segno /		\
 	  (sbi)->segs_per_sec) ||	\
 	 ((secno) == CURSEG_I(sbi, CURSEG_COLD_DATA_PINNED)->segno /	\
+	  (sbi)->segs_per_sec) ||	\
+	 ((secno) == CURSEG_I(sbi, CURSEG_ALL_DATA_ATGC)->segno /	\
 	  (sbi)->segs_per_sec))
 
 #define MAIN_BLKADDR(sbi)						\
@@ -135,20 +144,25 @@ enum {
  * In the victim_sel_policy->alloc_mode, there are two block allocation modes.
  * LFS writes data sequentially with cleaning operations.
  * SSR (Slack Space Recycle) reuses obsolete space without cleaning operations.
+ * AT_SSR (Age Threshold based Slack Space Recycle) merges fragments into
+ * fragmented segment which has similar aging degree.
  */
 enum {
 	LFS = 0,
-	SSR
+	SSR,
+	AT_SSR,
 };
 
 /*
  * In the victim_sel_policy->gc_mode, there are two gc, aka cleaning, modes.
  * GC_CB is based on cost-benefit algorithm.
  * GC_GREEDY is based on greedy algorithm.
+ * GC_AT is based on age-threshold algorithm.
  */
 enum {
 	GC_CB = 0,
 	GC_GREEDY,
+	GC_AT,
 	ALLOC_NEXT,
 	FLUSH_DEVICE,
 	MAX_GC_POLICY,
@@ -177,7 +191,10 @@ struct victim_sel_policy {
 	unsigned int offset;		/* last scanned bitmap offset */
 	unsigned int ofs_unit;		/* bitmap search unit */
 	unsigned int min_cost;		/* minimum cost */
+	unsigned long long oldest_age;	/* oldest age of segments having the same min cost */
 	unsigned int min_segno;		/* segment # having min. cost */
+	unsigned long long age;		/* mtime of GCed section*/
+	unsigned long long age_threshold;/* age threshold */
 };
 
 struct seg_entry {
@@ -243,6 +260,8 @@ struct sit_info {
 	unsigned long long mounted_time;	/* mount time */
 	unsigned long long min_mtime;		/* min. modification time */
 	unsigned long long max_mtime;		/* max. modification time */
+	unsigned long long dirty_min_mtime;	/* rerange candidates in GC_AT */
+	unsigned long long dirty_max_mtime;	/* rerange candidates in GC_AT */
 
 	unsigned int last_victim[MAX_GC_POLICY]; /* last victim segment # */
 };
@@ -281,7 +300,7 @@ struct dirty_seglist_info {
 /* victim selection function for cleaning and SSR */
 struct victim_selection {
 	int (*get_victim)(struct f2fs_sb_info *, unsigned int *,
-							int, int, char);
+					int, int, char, unsigned long long);
 };
 
 /* for active log information */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 426d6578d2c9..f3a07921d4f7 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -146,6 +146,7 @@ enum {
 	Opt_compress_algorithm,
 	Opt_compress_log_size,
 	Opt_compress_extension,
+	Opt_atgc,
 	Opt_err,
 };
 
@@ -213,6 +214,7 @@ static match_table_t f2fs_tokens = {
 	{Opt_compress_algorithm, "compress_algorithm=%s"},
 	{Opt_compress_log_size, "compress_log_size=%u"},
 	{Opt_compress_extension, "compress_extension=%s"},
+	{Opt_atgc, "atgc"},
 	{Opt_err, NULL},
 };
 
@@ -939,6 +941,9 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
 			f2fs_info(sbi, "compression options not supported");
 			break;
 #endif
+		case Opt_atgc:
+			set_opt(sbi, ATGC);
+			break;
 		default:
 			f2fs_err(sbi, "Unrecognized mount option \"%s\" or missing value",
 				 p);
@@ -1636,6 +1641,9 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 #ifdef CONFIG_F2FS_FS_COMPRESSION
 	f2fs_show_compress_options(seq, sbi->sb);
 #endif
+
+	if (test_opt(sbi, ATGC))
+		seq_puts(seq, ",atgc");
 	return 0;
 }
 
@@ -1765,6 +1773,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	bool no_extent_cache = !test_opt(sbi, EXTENT_CACHE);
 	bool disable_checkpoint = test_opt(sbi, DISABLE_CHECKPOINT);
 	bool no_io_align = !F2FS_IO_ALIGNED(sbi);
+	bool no_atgc = !test_opt(sbi, ATGC);
 	bool checkpoint_changed;
 #ifdef CONFIG_QUOTA
 	int i, j;
@@ -1837,6 +1846,13 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		}
 	}
 #endif
+	/* disallow enable atgc dynamically */
+	if (no_atgc == !!test_opt(sbi, ATGC)) {
+		err = -EINVAL;
+		f2fs_warn(sbi, "switch atgc option is not allowed");
+		goto restore_opts;
+	}
+
 	/* disallow enable/disable extent_cache dynamically */
 	if (no_extent_cache == !!test_opt(sbi, EXTENT_CACHE)) {
 		err = -EINVAL;
@@ -3792,6 +3808,8 @@ try_onemore:
 	}
 
 reset_checkpoint:
+	f2fs_init_inmem_curseg(sbi);
+
 	/* f2fs_recover_fsync_data() cleared this already */
 	clear_sbi_flag(sbi, SBI_POR_DOING);
 
@@ -3997,9 +4015,12 @@ static int __init init_f2fs_fs(void)
 	err = f2fs_create_extent_cache();
 	if (err)
 		goto free_checkpoint_caches;
-	err = f2fs_init_sysfs();
+	err = f2fs_create_garbage_collection_cache();
 	if (err)
 		goto free_extent_cache;
+	err = f2fs_init_sysfs();
+	if (err)
+		goto free_garbage_collection_cache;
 	err = register_shrinker(&f2fs_shrinker_info);
 	if (err)
 		goto free_sysfs;
@@ -4033,6 +4054,8 @@ free_shrinker:
 	unregister_shrinker(&f2fs_shrinker_info);
 free_sysfs:
 	f2fs_exit_sysfs();
+free_garbage_collection_cache:
+	f2fs_destroy_garbage_collection_cache();
 free_extent_cache:
 	f2fs_destroy_extent_cache();
 free_checkpoint_caches:
@@ -4057,6 +4080,7 @@ static void __exit exit_f2fs_fs(void)
 	unregister_filesystem(&f2fs_fs_type);
 	unregister_shrinker(&f2fs_shrinker_info);
 	f2fs_exit_sysfs();
+	f2fs_destroy_garbage_collection_cache();
 	f2fs_destroy_extent_cache();
 	f2fs_destroy_checkpoint_caches();
 	f2fs_destroy_segment_manager_caches();
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 70ad87d5492f..94c98e412aa1 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -377,12 +377,17 @@ out:
 		return count;
 	}
 	if (!strcmp(a->attr.name, "gc_idle")) {
-		if (t == GC_IDLE_CB)
+		if (t == GC_IDLE_CB) {
 			sbi->gc_mode = GC_IDLE_CB;
-		else if (t == GC_IDLE_GREEDY)
+		} else if (t == GC_IDLE_GREEDY) {
 			sbi->gc_mode = GC_IDLE_GREEDY;
-		else
+		} else if (t == GC_IDLE_AT) {
+			if (!sbi->am.atgc_enabled)
+				return -EINVAL;
+			sbi->gc_mode = GC_AT;
+		} else {
 			sbi->gc_mode = GC_NORMAL;
+		}
 		return count;
 	}
 
diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
index 8a1c1311acac..06c73f3f6dd2 100644
--- a/include/trace/events/f2fs.h
+++ b/include/trace/events/f2fs.h
@@ -111,13 +111,15 @@ TRACE_DEFINE_ENUM(CP_RESIZE);
 
 #define show_alloc_mode(type)						\
 	__print_symbolic(type,						\
-		{ LFS,	"LFS-mode" },					\
-		{ SSR,	"SSR-mode" })
+		{ LFS,		"LFS-mode" },				\
+		{ SSR,		"SSR-mode" },				\
+		{ AT_SSR,	"AT_SSR-mode" })
 
 #define show_victim_policy(type)					\
 	__print_symbolic(type,						\
 		{ GC_GREEDY,	"Greedy" },				\
-		{ GC_CB,	"Cost-Benefit" })
+		{ GC_CB,	"Cost-Benefit" },			\
+		{ GC_AT,	"Age-threshold" })
 
 #define show_cpreason(type)						\
 	__print_flags(type, "|",					\