f2fs: readahead node blocks in F2FS_GET_BLOCK_PRECACHE mode
In f2fs_precache_extents(), For large files, It requires reading many
node blocks. Instead of reading each node block with synchronous I/O,
this patch applies readahead so that node blocks can be fetched in
advance.
It reduces the overhead of repeated sync reads and improves efficiency
when precaching extents of large files.
I created a file with the same largest extent and executed the test.
For this experiment, I set the file's largest extent with an offset of 0
and a size of 1GB. I configured the remaining area with 100MB extents.
5GB test file:
dd if=/dev/urandom of=test1 bs=1m count=5120
cp test1 test2
fsync test1
dd if=test1 of=test2 bs=1m skip=1024 seek=1024 count=100 conv=notrunc
dd if=test1 of=test2 bs=1m skip=1224 seek=1224 count=100 conv=notrunc
...
dd if=test1 of=test2 bs=1m skip=5024 seek=5024 count=100 conv=notrunc
reboot
I also created 10GB and 20GB files with large extents using the same
method.
ioctl(F2FS_IOC_PRECACHE_EXTENTS) test results are as follows:
+-----------+---------+---------+-----------+
| File size | Before | After | Reduction |
+-----------+---------+---------+-----------+
| 5GB | 101.8ms | 37.0ms | 72.1% |
| 10GB | 222.9ms | 56.0ms | 74.9% |
| 20GB | 446.2ms | 116.4ms | 73.9% |
+-----------+---------+---------+-----------+
Tested on a 256GB mobile device with an SM8750 chipset.
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: Sunmin Jeong <s_min.jeong@samsung.com>
Signed-off-by: Yunji Kang <yunji0.kang@samsung.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 3a974e2..ed90b2c 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1565,6 +1565,9 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
pgofs = (pgoff_t)map->m_lblk;
end = pgofs + maxblocks;
+ if (flag == F2FS_GET_BLOCK_PRECACHE)
+ mode = LOOKUP_NODE_RA;
+
next_dnode:
if (map->m_may_create) {
if (f2fs_lfs_mode(sbi))
