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Both nat_bits cache and free_nid_bitmap cache provide same functionality
as a intermediate cache between free nid cache and disk, but with
different granularity of indicating free nid range, and different
persistence policy. nat_bits cache provides better persistence ability,
and free_nid_bitmap provides better granularity.
In this patch we combine advantage of both caches, so finally policy of
the intermediate cache would be:
- init: load free nid status from nat_bits into free_nid_bitmap
- lookup: scan free_nid_bitmap before load NAT blocks
- update: update free_nid_bitmap in real-time
- persistence: udpate and persist nat_bits in checkpoint
This patch also resolves performance regression reported by lkp-robot.
commit:
4ac912427c4214d8031d9ad6fbc3bc75e71512df ("f2fs: introduce free nid bitmap")
d00030cf9cd0bb96fdccc41e33d3c91dcbb672ba ("f2fs: use __set{__clear}_bit_le")
1382c0f3f9d3f936c8bc42ed1591cf7a593ef9f7 ("f2fs: combine nat_bits and free_nid_bitmap cache")
4ac912427c4214d8 d00030cf9cd0bb96fdccc41e33 1382c0f3f9d3f936c8bc42ed15
---------------- -------------------------- --------------------------
%stddev %change %stddev %change %stddev
\ | \ | \
77863 ± 0% +2.1% 79485 ± 1% +50.8% 117404 ± 0% aim7.jobs-per-min
231.63 ± 0% -2.0% 227.01 ± 1% -33.6% 153.80 ± 0% aim7.time.elapsed_time
231.63 ± 0% -2.0% 227.01 ± 1% -33.6% 153.80 ± 0% aim7.time.elapsed_time.max
896604 ± 0% -0.8% 889221 ± 3% -20.2% 715260 ± 1% aim7.time.involuntary_context_switches
2394 ± 1% +4.6% 2503 ± 1% +3.7% 2481 ± 2% aim7.time.maximum_resident_set_size
6240 ± 0% -1.5% 6145 ± 1% -14.1% 5360 ± 1% aim7.time.system_time
1111357 ± 3% +1.9% 1132509 ± 2% -6.2% 1041932 ± 2% aim7.time.voluntary_context_switches
...
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Tested-by: Xiaolong Ye <xiaolong.ye@intel.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.