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Diffstat (limited to 'Documentation/filesystems/f2fs.txt')
| -rw-r--r-- | Documentation/filesystems/f2fs.txt | 216 |
1 files changed, 52 insertions, 164 deletions
diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt index 3135b80df6da..4eb3e2ddd00e 100644 --- a/Documentation/filesystems/f2fs.txt +++ b/Documentation/filesystems/f2fs.txt @@ -235,6 +235,17 @@ checkpoint=%s[:%u[%]] Set to "disable" to turn off checkpointing. Set to "en hide up to all remaining free space. The actual space that would be unusable can be viewed at /sys/fs/f2fs/<disk>/unusable This space is reclaimed once checkpoint=enable. +compress_algorithm=%s Control compress algorithm, currently f2fs supports "lzo" + and "lz4" algorithm. +compress_log_size=%u Support configuring compress cluster size, the size will + be 4KB * (1 << %u), 16KB is minimum size, also it's + default size. +compress_extension=%s Support adding specified extension, so that f2fs can enable + compression on those corresponding files, e.g. if all files + with '.ext' has high compression rate, we can set the '.ext' + on compression extension list and enable compression on + these file by default rather than to enable it via ioctl. + For other files, we can still enable compression via ioctl. ================================================================================ DEBUGFS ENTRIES @@ -259,170 +270,6 @@ The files in each per-device directory are shown in table below. Files in /sys/fs/f2fs/<devname> (see also Documentation/ABI/testing/sysfs-fs-f2fs) -.............................................................................. - File Content - - gc_urgent_sleep_time This parameter controls sleep time for gc_urgent. - 500 ms is set by default. See above gc_urgent. - - gc_min_sleep_time This tuning parameter controls the minimum sleep - time for the garbage collection thread. Time is - in milliseconds. - - gc_max_sleep_time This tuning parameter controls the maximum sleep - time for the garbage collection thread. Time is - in milliseconds. - - gc_no_gc_sleep_time This tuning parameter controls the default sleep - time for the garbage collection thread. Time is - in milliseconds. - - gc_idle This parameter controls the selection of victim - policy for garbage collection. Setting gc_idle = 0 - (default) will disable this option. Setting - gc_idle = 1 will select the Cost Benefit approach - & setting gc_idle = 2 will select the greedy approach. - - gc_urgent This parameter controls triggering background GCs - urgently or not. Setting gc_urgent = 0 [default] - makes back to default behavior, while if it is set - to 1, background thread starts to do GC by given - gc_urgent_sleep_time interval. - - reclaim_segments This parameter controls the number of prefree - segments to be reclaimed. If the number of prefree - segments is larger than the number of segments - in the proportion to the percentage over total - volume size, f2fs tries to conduct checkpoint to - reclaim the prefree segments to free segments. - By default, 5% over total # of segments. - - main_blkaddr This value gives the first block address of - MAIN area in the partition. - - max_small_discards This parameter controls the number of discard - commands that consist small blocks less than 2MB. - The candidates to be discarded are cached until - checkpoint is triggered, and issued during the - checkpoint. By default, it is disabled with 0. - - discard_granularity This parameter controls the granularity of discard - command size. It will issue discard commands iif - the size is larger than given granularity. Its - unit size is 4KB, and 4 (=16KB) is set by default. - The maximum value is 128 (=512KB). - - reserved_blocks This parameter indicates the number of blocks that - f2fs reserves internally for root. - - batched_trim_sections This parameter controls the number of sections - to be trimmed out in batch mode when FITRIM - conducts. 32 sections is set by default. - - ipu_policy This parameter controls the policy of in-place - updates in f2fs. There are five policies: - 0x01: F2FS_IPU_FORCE, 0x02: F2FS_IPU_SSR, - 0x04: F2FS_IPU_UTIL, 0x08: F2FS_IPU_SSR_UTIL, - 0x10: F2FS_IPU_FSYNC. - - min_ipu_util This parameter controls the threshold to trigger - in-place-updates. The number indicates percentage - of the filesystem utilization, and used by - F2FS_IPU_UTIL and F2FS_IPU_SSR_UTIL policies. - - min_fsync_blocks This parameter controls the threshold to trigger - in-place-updates when F2FS_IPU_FSYNC mode is set. - The number indicates the number of dirty pages - when fsync needs to flush on its call path. If - the number is less than this value, it triggers - in-place-updates. - - min_seq_blocks This parameter controls the threshold to serialize - write IOs issued by multiple threads in parallel. - - min_hot_blocks This parameter controls the threshold to allocate - a hot data log for pending data blocks to write. - - min_ssr_sections This parameter adds the threshold when deciding - SSR block allocation. If this is large, SSR mode - will be enabled early. - - ram_thresh This parameter controls the memory footprint used - by free nids and cached nat entries. By default, - 1 is set, which indicates 10 MB / 1 GB RAM. - - ra_nid_pages When building free nids, F2FS reads NAT blocks - ahead for speed up. Default is 0. - - dirty_nats_ratio Given dirty ratio of cached nat entries, F2FS - determines flushing them in background. - - max_victim_search This parameter controls the number of trials to - find a victim segment when conducting SSR and - cleaning operations. The default value is 4096 - which covers 8GB block address range. - - migration_granularity For large-sized sections, F2FS can stop GC given - this granularity instead of reclaiming entire - section. - - dir_level This parameter controls the directory level to - support large directory. If a directory has a - number of files, it can reduce the file lookup - latency by increasing this dir_level value. - Otherwise, it needs to decrease this value to - reduce the space overhead. The default value is 0. - - cp_interval F2FS tries to do checkpoint periodically, 60 secs - by default. - - idle_interval F2FS detects system is idle, if there's no F2FS - operations during given interval, 5 secs by - default. - - discard_idle_interval F2FS detects the discard thread is idle, given - time interval. Default is 5 secs. - - gc_idle_interval F2FS detects the GC thread is idle, given time - interval. Default is 5 secs. - - umount_discard_timeout When unmounting the disk, F2FS waits for finishing - queued discard commands which can take huge time. - This gives time out for it, 5 secs by default. - - iostat_enable This controls to enable/disable iostat in F2FS. - - readdir_ra This enables/disabled readahead of inode blocks - in readdir, and default is enabled. - - gc_pin_file_thresh This indicates how many GC can be failed for the - pinned file. If it exceeds this, F2FS doesn't - guarantee its pinning state. 2048 trials is set - by default. - - extension_list This enables to change extension_list for hot/cold - files in runtime. - - inject_rate This controls injection rate of arbitrary faults. - - inject_type This controls injection type of arbitrary faults. - - dirty_segments This shows # of dirty segments. - - lifetime_write_kbytes This shows # of data written to the disk. - - features This shows current features enabled on F2FS. - - current_reserved_blocks This shows # of blocks currently reserved. - - unusable If checkpoint=disable, this shows the number of - blocks that are unusable. - If checkpoint=enable it shows the number of blocks - that would be unusable if checkpoint=disable were - to be set. - -encoding This shows the encoding used for casefolding. - If casefolding is not enabled, returns (none) ================================================================================ USAGE @@ -840,3 +687,44 @@ zero or random data, which is useful to the below scenario where: 4. address = fibmap(fd, offset) 5. open(blkdev) 6. write(blkdev, address) + +Compression implementation +-------------------------- + +- New term named cluster is defined as basic unit of compression, file can +be divided into multiple clusters logically. One cluster includes 4 << n +(n >= 0) logical pages, compression size is also cluster size, each of +cluster can be compressed or not. + +- In cluster metadata layout, one special block address is used to indicate +cluster is compressed one or normal one, for compressed cluster, following +metadata maps cluster to [1, 4 << n - 1] physical blocks, in where f2fs +stores data including compress header and compressed data. + +- In order to eliminate write amplification during overwrite, F2FS only +support compression on write-once file, data can be compressed only when +all logical blocks in file are valid and cluster compress ratio is lower +than specified threshold. + +- To enable compression on regular inode, there are three ways: +* chattr +c file +* chattr +c dir; touch dir/file +* mount w/ -o compress_extension=ext; touch file.ext + +Compress metadata layout: + [Dnode Structure] + +-----------------------------------------------+ + | cluster 1 | cluster 2 | ......... | cluster N | + +-----------------------------------------------+ + . . . . + . . . . + . Compressed Cluster . . Normal Cluster . ++----------+---------+---------+---------+ +---------+---------+---------+---------+ +|compr flag| block 1 | block 2 | block 3 | | block 1 | block 2 | block 3 | block 4 | ++----------+---------+---------+---------+ +---------+---------+---------+---------+ + . . + . . + . . + +-------------+-------------+----------+----------------------------+ + | data length | data chksum | reserved | compressed data | + +-------------+-------------+----------+----------------------------+ |