mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git
synced 2024-11-23 17:53:39 +08:00
03aa49e495
Overview
========
This option allows zoned block device users to configure GC reserved and
overprovision area manually according to their demands on performance of
sustained write latency and WAF.
Problem
=======
The overprovision segments that mkfs generates are mostly occupied by GC
reserved. This degrades WAF performance.
Experiment
==========
The following experiment evaluated the application of configurable reserved.
The experimental environment is as follows.
System info
- 4.2Ghz, 8 core CPU
- 64GiB Memory
Device info
- a conventional null_blk with 448MiB capacity(meta area) and
- a sequential null_blk with 953 zones of 64MiB
Format
- as-is (find out ovp ratio): mkfs.f2fs <conv null_blk> -c <seq null_blk> -m
Info: Overprovision ratio = 3.700%
Info: Overprovision segments = 1152 (GC reserved = 1088)
- config rsvd: mkfs.f2fs <conv null_blk> -c <seq null_blk> -m -Z 8 -o 2.965
Info: Overprovision ratio = 2.965%
Info: Overprovision segments = 1152 (GC reserved = 256)
Mount
- mount <conv null_blk> <mount point>
Fio script
- fio --rw=randwrite --bs=4k --ba=4k --filesize=58630m --norandommap --overwrite=1 --name=job1 --filename=<mount point>/sustain --time_based --runtime=2h
WAF calculation
- (IOs on conv. null_blk + IOs on seq. null_blk) / random write IOs
Conclusion
==========
In the experiment, it can be shown that reducing the reserved segments
decreases WAF to 10% (from 222 to 23) although it triggers checkpoint more
frequently during gc. With direct IO, the WAF of as-is gets much higher.
In other words, a user can configure more reserved segments for lower GC
latency or allocate less reserved segments for lower WAF on the same number
of OP segments.
Signed-off-by: Yonggil Song <yonggil.song@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
|
||
|---|---|---|
| .. | ||
| android_config.h | ||
| f2fs_fs.h | ||
| quota.h | ||