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, 14 insertions, 0 deletions

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 412c2e7352c0..180d8b804d13 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -163,6 +163,7 @@ enum {
 	Opt_nogc_merge,
 	Opt_discard_unit,
 	Opt_memory_mode,
+	Opt_age_extent_cache,
 	Opt_err,
 };
 
@@ -241,6 +242,7 @@ static match_table_t f2fs_tokens = {
 	{Opt_nogc_merge, "nogc_merge"},
 	{Opt_discard_unit, "discard_unit=%s"},
 	{Opt_memory_mode, "memory=%s"},
+	{Opt_age_extent_cache, "age_extent_cache"},
 	{Opt_err, NULL},
 };
 
@@ -1257,6 +1259,9 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
 			}
 			kfree(name);
 			break;
+		case Opt_age_extent_cache:
+			set_opt(sbi, AGE_EXTENT_CACHE);
+			break;
 		default:
 			f2fs_err(sbi, "Unrecognized mount option \"%s\" or missing value",
 				 p);
@@ -1958,6 +1963,8 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 		seq_puts(seq, ",extent_cache");
 	else
 		seq_puts(seq, ",noextent_cache");
+	if (test_opt(sbi, AGE_EXTENT_CACHE))
+		seq_puts(seq, ",age_extent_cache");
 	if (test_opt(sbi, DATA_FLUSH))
 		seq_puts(seq, ",data_flush");
 
@@ -2219,6 +2226,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	bool need_restart_flush = false, need_stop_flush = false;
 	bool need_restart_discard = false, need_stop_discard = false;
 	bool no_read_extent_cache = !test_opt(sbi, READ_EXTENT_CACHE);
+	bool no_age_extent_cache = !test_opt(sbi, AGE_EXTENT_CACHE);
 	bool enable_checkpoint = !test_opt(sbi, DISABLE_CHECKPOINT);
 	bool no_io_align = !F2FS_IO_ALIGNED(sbi);
 	bool no_atgc = !test_opt(sbi, ATGC);
@@ -2313,6 +2321,12 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		f2fs_warn(sbi, "switch extent_cache option is not allowed");
 		goto restore_opts;
 	}
+	/* disallow enable/disable age extent_cache dynamically */
+	if (no_age_extent_cache == !!test_opt(sbi, AGE_EXTENT_CACHE)) {
+		err = -EINVAL;
+		f2fs_warn(sbi, "switch age_extent_cache option is not allowed");
+		goto restore_opts;
+	}
 
 	if (no_io_align == !!F2FS_IO_ALIGNED(sbi)) {
 		err = -EINVAL;