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| author | Daeho Jeong <daehojeong@google.com> | 2021-09-29 20:12:03 +0200 |
|---|---|---|
| committer | Jaegeuk Kim <jaegeuk@kernel.org> | 2021-10-26 23:04:30 +0200 |
| commit | 6691d940b0e09dd1564130e7a354d6deaf05d009 (patch) | |
| tree | ae609ea58abdfd7ce7c73e72f82d39226f2de3a9 /Documentation | |
| parent | f2fs: replace snprintf in show functions with sysfs_emit (diff) | |
| download | linux-6691d940b0e09dd1564130e7a354d6deaf05d009.tar.xz linux-6691d940b0e09dd1564130e7a354d6deaf05d009.zip | |
f2fs: introduce fragment allocation mode mount option
Added two options into "mode=" mount option to make it possible for
developers to simulate filesystem fragmentation/after-GC situation
itself. The developers use these modes to understand filesystem
fragmentation/after-GC condition well, and eventually get some
insights to handle them better.
"fragment:segment": f2fs allocates a new segment in ramdom position.
With this, we can simulate the after-GC condition.
"fragment:block" : We can scatter block allocation with
"max_fragment_chunk" and "max_fragment_hole" sysfs
nodes. f2fs will allocate 1..<max_fragment_chunk>
blocks in a chunk and make a hole in the length of
1..<max_fragment_hole> by turns in a newly allocated
free segment. Plus, this mode implicitly enables
"fragment:segment" option for more randomness.
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-fs-f2fs | 16 | ||||
| -rw-r--r-- | Documentation/filesystems/f2fs.rst | 18 |
2 files changed, 34 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs index f627e705e663..b268e3e18b4a 100644 --- a/Documentation/ABI/testing/sysfs-fs-f2fs +++ b/Documentation/ABI/testing/sysfs-fs-f2fs @@ -512,3 +512,19 @@ Date: July 2021 Contact: "Daeho Jeong" <daehojeong@google.com> Description: You can control the multiplier value of bdi device readahead window size between 2 (default) and 256 for POSIX_FADV_SEQUENTIAL advise option. + +What: /sys/fs/f2fs/<disk>/max_fragment_chunk +Date: August 2021 +Contact: "Daeho Jeong" <daehojeong@google.com> +Description: With "mode=fragment:block" mount options, we can scatter block allocation. + f2fs will allocate 1..<max_fragment_chunk> blocks in a chunk and make a hole + in the length of 1..<max_fragment_hole> by turns. This value can be set + between 1..512 and the default value is 4. + +What: /sys/fs/f2fs/<disk>/max_fragment_hole +Date: August 2021 +Contact: "Daeho Jeong" <daehojeong@google.com> +Description: With "mode=fragment:block" mount options, we can scatter block allocation. + f2fs will allocate 1..<max_fragment_chunk> blocks in a chunk and make a hole + in the length of 1..<max_fragment_hole> by turns. This value can be set + between 1..512 and the default value is 4. diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst index 09de6ebbbdfa..4294db649fa8 100644 --- a/Documentation/filesystems/f2fs.rst +++ b/Documentation/filesystems/f2fs.rst @@ -201,6 +201,24 @@ fault_type=%d Support configuring fault injection type, should be mode=%s Control block allocation mode which supports "adaptive" and "lfs". In "lfs" mode, there should be no random writes towards main area. + "fragment:segment" and "fragment:block" are newly added here. + These are developer options for experiments to simulate filesystem + fragmentation/after-GC situation itself. The developers use these + modes to understand filesystem fragmentation/after-GC condition well, + and eventually get some insights to handle them better. + In "fragment:segment", f2fs allocates a new segment in ramdom + position. With this, we can simulate the after-GC condition. + In "fragment:block", we can scatter block allocation with + "max_fragment_chunk" and "max_fragment_hole" sysfs nodes. + We added some randomness to both chunk and hole size to make + it close to realistic IO pattern. So, in this mode, f2fs will allocate + 1..<max_fragment_chunk> blocks in a chunk and make a hole in the + length of 1..<max_fragment_hole> by turns. With this, the newly + allocated blocks will be scattered throughout the whole partition. + Note that "fragment:block" implicitly enables "fragment:segment" + option for more randomness. + Please, use these options for your experiments and we strongly + recommend to re-format the filesystem after using these options. io_bits=%u Set the bit size of write IO requests. It should be set with "mode=lfs". usrquota Enable plain user disk quota accounting. |