f2fs: add block_age-based extent cache

This patch introduces a runtime hot/cold data separation method
for f2fs, in order to improve the accuracy for data temperature
classification, reduce the garbage collection overhead after
long-term data updates.

Enhanced hot/cold data separation can record data block update
frequency as "age" of the extent per inode, and take use of the age
info to indicate better temperature type for data block allocation:
 - It records total data blocks allocated since mount;
 - When file extent has been updated, it calculate the count of data
blocks allocated since last update as the age of the extent;
 - Before the data block allocated, it searches for the age info and
chooses the suitable segment for allocation.

Test and result:
 - Prepare: create about 30000 files
  * 3% for cold files (with cold file extension like .apk, from 3M to 10M)
  * 50% for warm files (with random file extension like .FcDxq, from 1K
to 4M)
  * 47% for hot files (with hot file extension like .db, from 1K to 256K)
 - create(5%)/random update(90%)/delete(5%) the files
  * total write amount is about 70G
  * fsync will be called for .db files, and buffered write will be used
for other files

The storage of test device is large enough(128G) so that it will not
switch to SSR mode during the test.

Benefit: dirty segment count increment reduce about 14%
 - before: Dirty +21110
 - after:  Dirty +18286

Signed-off-by: qixiaoyu1 <qixiaoyu1@xiaomi.com>
Signed-off-by: xiongping1 <xiongping1@xiaomi.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index ec52e06f8e61..e8953c3dc81a 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -107,6 +107,7 @@ extern const char *f2fs_fault_name[FAULT_MAX];
 #define F2FS_MOUNT_MERGE_CHECKPOINT	0x10000000
 #define	F2FS_MOUNT_GC_MERGE		0x20000000
 #define F2FS_MOUNT_COMPRESS_CACHE	0x40000000
+#define F2FS_MOUNT_AGE_EXTENT_CACHE	0x80000000
 
 #define F2FS_OPTION(sbi)	((sbi)->mount_opt)
 #define clear_opt(sbi, option)	(F2FS_OPTION(sbi).opt &= ~F2FS_MOUNT_##option)
@@ -607,9 +608,22 @@ enum {
 /* number of extent info in extent cache we try to shrink */
 #define READ_EXTENT_CACHE_SHRINK_NUMBER	128
 
+/* number of age extent info in extent cache we try to shrink */
+#define AGE_EXTENT_CACHE_SHRINK_NUMBER	128
+#define LAST_AGE_WEIGHT			30
+#define SAME_AGE_REGION			1024
+
+/*
+ * Define data block with age less than 1GB as hot data
+ * define data block with age less than 10GB but more than 1GB as warm data
+ */
+#define DEF_HOT_DATA_AGE_THRESHOLD	262144
+#define DEF_WARM_DATA_AGE_THRESHOLD	2621440
+
 /* extent cache type */
 enum extent_type {
 	EX_READ,
+	EX_BLOCK_AGE,
 	NR_EXTENT_CACHES,
 };
 
@@ -637,6 +651,13 @@ struct extent_info {
 			unsigned int c_len;
 #endif
 		};
+		/* block age extent_cache */
+		struct {
+			/* block age of the extent */
+			unsigned long long age;
+			/* last total blocks allocated */
+			unsigned long long last_blocks;
+		};
 	};
 };
 
@@ -1653,6 +1674,11 @@ struct f2fs_sb_info {
 
 	/* for extent tree cache */
 	struct extent_tree_info extent_tree[NR_EXTENT_CACHES];
+	atomic64_t allocated_data_blocks;	/* for block age extent_cache */
+
+	/* The threshold used for hot and warm data seperation*/
+	unsigned int hot_data_age_threshold;
+	unsigned int warm_data_age_threshold;
 
 	/* basic filesystem units */
 	unsigned int log_sectors_per_block;	/* log2 sectors per block */
@@ -3857,6 +3883,8 @@ struct f2fs_stat_info {
 	unsigned long long ext_mem[NR_EXTENT_CACHES];
 	/* for read extent cache */
 	unsigned long long hit_largest;
+	/* for block age extent cache */
+	unsigned long long allocated_data_blocks;
 	int ndirty_node, ndirty_dent, ndirty_meta, ndirty_imeta;
 	int ndirty_data, ndirty_qdata;
 	unsigned int ndirty_dirs, ndirty_files, nquota_files, ndirty_all;
@@ -4168,6 +4196,16 @@ void f2fs_update_read_extent_cache_range(struct dnode_of_data *dn,
 unsigned int f2fs_shrink_read_extent_tree(struct f2fs_sb_info *sbi,
 			int nr_shrink);
 
+/* block age extent cache ops */
+void f2fs_init_age_extent_tree(struct inode *inode);
+bool f2fs_lookup_age_extent_cache(struct inode *inode, pgoff_t pgofs,
+			struct extent_info *ei);
+void f2fs_update_age_extent_cache(struct dnode_of_data *dn);
+void f2fs_update_age_extent_cache_range(struct dnode_of_data *dn,
+			pgoff_t fofs, unsigned int len);
+unsigned int f2fs_shrink_age_extent_tree(struct f2fs_sb_info *sbi,
+			int nr_shrink);
+
 /*
  * sysfs.c
  */