Lines Matching +full:cpu +full:- +full:capacity
1 .. SPDX-License-Identifier: GPL-2.0
4 WHAT IS Flash-Friendly File System (F2FS)?
7 NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have
13 F2FS is a file system exploiting NAND flash memory-based storage devices, which
14 is based on Log-structured File System (LFS). The design has been focused on
18 Since a NAND flash memory-based storage device shows different characteristic
20 F2FS and its tools support various parameters not only for configuring on-disk
26 - git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git
30 - linux-f2fs-devel@lists.sourceforge.net
35 Log-structured File System (LFS)
36 --------------------------------
37 "A log-structured file system writes all modifications to disk sequentially in
38 a log-like structure, thereby speeding up both file writing and crash recovery.
44 implementation of a log-structured file system", ACM Trans. Computer Systems
48 ----------------------
57 [1] Bityutskiy, A. 2005. JFFS3 design issues. http://www.linux-mtd.infradead.org/
60 -----------------
61 Since LFS is based on out-of-place writes, it produces so many obsolete blocks
71 3. It checks the cross-reference between the data and its parent index structure.
82 ---------------
83 - Enlarge the random write area for better performance, but provide the high
85 - Align FS data structures to the operational units in FTL as best efforts
88 ----------------------
89 - Use a term, “node”, that represents inodes as well as various pointer blocks
90 - Introduce Node Address Table (NAT) containing the locations of all the “node”
94 -----------------
95 - Support a background cleaning process
96 - Support greedy and cost-benefit algorithms for victim selection policies
97 - Support multi-head logs for static/dynamic hot and cold data separation
98 - Introduce adaptive logging for efficient block allocation
117 I/O and CPU resources.
119 disable_roll_forward Disable the roll-forward recovery routine
120 norecovery Disable the roll-forward recovery routine, mounted read-
121 only (i.e., -o ro,disable_roll_forward)
122 discard/nodiscard Enable/disable real-time discard in f2fs, if discard is
125 no_heap Disable heap-style segment allocation which finds free
160 extent_cache Enable an extent cache based on rb-tree, it can cache
164 noextent_cache Disable an extent cache based on rb-tree explicitly, see
217 layer. This supports "off", "user-based", and
218 "fs-based". In "off" mode (default), f2fs does not pass
219 down hints. In "user-based" mode, f2fs tries to pass
220 down hints given by users. And in "fs-based" mode, f2fs
232 non-atomic files likewise "nobarrier" mount option.
260 a cgroup having low i/o budget and cpu shares. To make this
267 "lz4", "zstd" and "lzo-rle" algorithm.
271 lz4 3 - 16
272 zstd 1 - 22
296 files using the blk-crypto framework rather than
297 filesystem-layer encryption. This allows the use of
298 inline encryption hardware. The on-disk format is
300 Documentation/block/inline-encryption.rst.
301 atgc Enable age-threshold garbage collection, it provides high
308 age_extent_cache Enable an age extent cache based on rb-tree. It records
322 - major file system information managed by f2fs currently
323 - average SIT information about whole segments
324 - current memory footprint consumed by f2fs.
332 The files in each per-device directory are shown in table below.
335 (see also Documentation/ABI/testing/sysfs-fs-f2fs)
353 # mkfs.f2fs -l label /dev/block_device
354 # mount -t f2fs /dev/block_device /mnt/f2fs
357 ---------
359 which builds a basic on-disk layout.
364 ``-l [label]`` Give a volume label, up to 512 unicode name.
365 ``-a [0 or 1]`` Split start location of each area for heap-based allocation.
368 ``-o [int]`` Set overprovision ratio in percent over volume size.
371 ``-s [int]`` Set the number of segments per section.
374 ``-z [int]`` Set the number of sections per zone.
377 ``-e [str]`` Set basic extension list. e.g. "mp3,gif,mov"
378 ``-t [0 or 1]`` Disable discard command or not.
386 ---------
387 The fsck.f2fs is a tool to check the consistency of an f2fs-formatted
388 partition, which examines whether the filesystem metadata and user-made data
389 are cross-referenced correctly or not.
394 -d debug level [default:0]
399 ---------
403 The dump.f2fs is used to debug on-disk data structures of the f2fs filesystem.
404 It shows on-disk inode information recognized by a given inode number, and is
410 -d debug level [default:0]
411 -i inode no (hex)
412 -s [SIT dump segno from #1~#2 (decimal), for all 0~-1]
413 -a [SSA dump segno from #1~#2 (decimal), for all 0~-1]
417 # dump.f2fs -i [ino] /dev/sdx
418 # dump.f2fs -s 0~-1 /dev/sdx (SIT dump)
419 # dump.f2fs -a 0~-1 /dev/sdx (SSA dump)
424 ----------
431 -----------
432 The resize.f2fs lets a user resize the f2fs-formatted disk image, while preserving
438 -----------
446 -------
448 f2fs-specific ones, which is very useful for QA tests.
455 On-disk Layout
456 --------------
466 align with the zone size <-|
467 |-> align with the segment size
485 - Superblock (SB)
490 - Checkpoint (CP)
494 - Segment Information Table (SIT)
498 - Node Address Table (NAT)
502 - Segment Summary Area (SSA)
506 - Main Area
509 In order to avoid misalignment between file system and flash-based storage, F2FS
518 ------------------------------
529 +--------+----------+---------+
531 +--------+----------+---------+
535 +-------+-------+--------+--------+--------+--------+
537 +-------+-------+--------+--------+--------+--------+
540 `----------------------------------------'
543 ---------------
556 |- data (923)
557 |- direct node (2)
558 | `- data (1018)
559 |- indirect node (2)
560 | `- direct node (1018)
561 | `- data (1018)
562 `- double indirect node (1)
563 `- indirect node (1018)
564 `- direct node (1018)
565 `- data (1018)
573 -------------------
577 - hash hash value of the file name
578 - ino inode number
579 - len the length of file name
580 - type file type such as directory, symlink, etc
592 +--------------------------------+
594 +--------------------------------+
598 +--------+----------+----------+------------+
600 +--------+----------+----------+------------+
604 +------+------+-----+------+
606 +------+------+-----+------+
609 F2FS implements multi-level hash tables for directory structure. Each level has
615 ----------------------
619 ----------------------
623 level #1 | A(2B) - A(2B)
625 level #2 | A(2B) - A(2B) - A(2B) - A(2B)
627 level #N/2 | A(2B) - A(2B) - A(2B) - A(2B) - A(2B) - ... - A(2B)
629 level #N | A(4B) - A(4B) - A(4B) - A(4B) - A(4B) - ... - A(4B)
633 ,- 2, if n < MAX_DIR_HASH_DEPTH / 2,
635 `- 4, Otherwise
637 ,- 2^(n + dir_level),
640 `- 2^((MAX_DIR_HASH_DEPTH / 2) - 1),
659 --------------> Dir <--------------
663 child - child [hole] - child
665 child - child - child [hole] - [hole] - child
672 ------------------------
677 - Hot node contains direct node blocks of directories.
678 - Warm node contains direct node blocks except hot node blocks.
679 - Cold node contains indirect node blocks
680 - Hot data contains dentry blocks
681 - Warm data contains data blocks except hot and cold data blocks
682 - Cold data contains multimedia data or migrated data blocks
684 LFS has two schemes for free space management: threaded log and copy-and-compac-
685 tion. The copy-and-compaction scheme which is known as cleaning, is well-suited
690 scheme where the copy-and-compaction scheme is adopted by default, but the
694 In order to align F2FS with underlying flash-based storage, F2FS allocates a
702 ----------------
704 F2FS does cleaning both on demand and in the background. On-demand cleaning is
709 F2FS supports two victim selection policies: greedy and cost-benefit algorithms.
711 of valid blocks. In the cost-benefit algorithm, F2FS selects a victim segment
714 algorithm for on-demand cleaner, while background cleaner adopts cost-benefit
721 Write-hint Policy
722 -----------------
726 2) whint_mode=user-based. F2FS tries to pass down hints given by
739 -- buffered io
747 -- direct io
756 3) whint_mode=fs-based. F2FS passes down hints with its policy.
768 -- buffered io
776 -- direct io
786 -------------------
801 fallocate(fd, DEFAULT_MODE), it allocates on-disk block addressess having
812 --------------------------
814 - New term named cluster is defined as basic unit of compression, file can
819 - In cluster metadata layout, one special block address is used to indicate
821 metadata maps cluster to [1, 4 << n - 1] physical blocks, in where f2fs
824 - In order to eliminate write amplification during overwrite, F2FS only
825 support compression on write-once file, data can be compressed only when
829 - To enable compression on regular inode, there are three ways:
833 * mount w/ -o compress_extension=ext; touch file.ext
834 * mount w/ -o compress_extension=*; touch any_file
836 - At this point, compression feature doesn't expose compressed space to user
846 +-----------------------------------------------+
848 +-----------------------------------------------+
852 +----------+---------+---------+---------+ +---------+---------+---------+---------+
854 +----------+---------+---------+---------+ +---------+---------+---------+---------+
858 +-------------+-------------+----------+----------------------------+
860 +-------------+-------------+----------+----------------------------+
863 --------------------------
891 ----------------------------
893 - ZNS defines a per-zone capacity which can be equal or less than the
894 zone-size. Zone-capacity is the number of usable blocks in the zone.
895 F2FS checks if zone-capacity is less than zone-size, if it is, then any
896 segment which starts after the zone-capacity is marked as not-free in
900 zone-capacity is not aligned to default segment size(2MB), then a segment
901 can start before the zone-capacity and span across zone-capacity boundary.
903 past the zone-capacity are considered unusable in these segments.