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Diffstat (limited to 'Documentation/filesystems/f2fs.txt')
| -rw-r--r-- | Documentation/filesystems/f2fs.txt | 133 |
1 files changed, 123 insertions, 10 deletions
diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt index f7b5e4ff0de3..496fa28b2492 100644 --- a/Documentation/filesystems/f2fs.txt +++ b/Documentation/filesystems/f2fs.txt @@ -214,11 +214,22 @@ fsync_mode=%s Control the policy of fsync. Currently supports "posix", non-atomic files likewise "nobarrier" mount option. test_dummy_encryption Enable dummy encryption, which provides a fake fscrypt context. The fake fscrypt context is used by xfstests. -checkpoint=%s Set to "disable" to turn off checkpointing. Set to "enable" +checkpoint=%s[:%u[%]] Set to "disable" to turn off checkpointing. Set to "enable" to reenable checkpointing. Is enabled by default. While disabled, any unmounting or unexpected shutdowns will cause the filesystem contents to appear as they did when the filesystem was mounted with that option. + While mounting with checkpoint=disabled, the filesystem must + run garbage collection to ensure that all available space can + be used. If this takes too much time, the mount may return + EAGAIN. You may optionally add a value to indicate how much + of the disk you would be willing to temporarily give up to + avoid additional garbage collection. This can be given as a + number of blocks, or as a percent. For instance, mounting + with checkpoint=disable:100% would always succeed, but it may + 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. ================================================================================ DEBUGFS ENTRIES @@ -246,11 +257,14 @@ Files in /sys/fs/f2fs/<devname> .............................................................................. File Content - gc_max_sleep_time This tuning parameter controls the maximum sleep + 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_min_sleep_time This tuning parameter controls the minimum sleep + gc_max_sleep_time This tuning parameter controls the maximum sleep time for the garbage collection thread. Time is in milliseconds. @@ -270,9 +284,6 @@ Files in /sys/fs/f2fs/<devname> to 1, background thread starts to do GC by given gc_urgent_sleep_time interval. - gc_urgent_sleep_time This parameter controls sleep time for gc_urgent. - 500 ms is set by default. See above gc_urgent. - 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 @@ -287,7 +298,16 @@ Files in /sys/fs/f2fs/<devname> checkpoint is triggered, and issued during the checkpoint. By default, it is disabled with 0. - trim_sections This parameter controls the number of sections + 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. @@ -309,11 +329,35 @@ Files in /sys/fs/f2fs/<devname> 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, + 10 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 @@ -321,9 +365,53 @@ Files in /sys/fs/f2fs/<devname> Otherwise, it needs to decrease this value to reduce the space overhead. The default value is 0. - ram_thresh This parameter controls the memory footprint used - by free nids and cached nat entries. By default, - 10 is set, which indicates 10 MB / 1 GB RAM. + 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. ================================================================================ USAGE @@ -716,3 +804,28 @@ WRITE_LIFE_NOT_SET WARM_DATA WRITE_LIFE_NOT_SET WRITE_LIFE_NONE " WRITE_LIFE_NONE WRITE_LIFE_MEDIUM " WRITE_LIFE_MEDIUM WRITE_LIFE_LONG " WRITE_LIFE_LONG + +Fallocate(2) Policy +------------------- + +The default policy follows the below posix rule. + +Allocating disk space + The default operation (i.e., mode is zero) of fallocate() allocates + the disk space within the range specified by offset and len. The + file size (as reported by stat(2)) will be changed if offset+len is + greater than the file size. Any subregion within the range specified + by offset and len that did not contain data before the call will be + initialized to zero. This default behavior closely resembles the + behavior of the posix_fallocate(3) library function, and is intended + as a method of optimally implementing that function. + +However, once F2FS receives ioctl(fd, F2FS_IOC_SET_PIN_FILE) in prior to +fallocate(fd, DEFAULT_MODE), it allocates on-disk blocks addressess having +zero or random data, which is useful to the below scenario where: + 1. create(fd) + 2. ioctl(fd, F2FS_IOC_SET_PIN_FILE) + 3. fallocate(fd, 0, 0, size) + 4. address = fibmap(fd, offset) + 5. open(blkdev) + 6. write(blkdev, address) |