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If we configure section consist of multiple segments, foreground GC will
do the garbage collection with following approach:
for each segment in victim section
blk_start_plug
for each valid block in segment
write out by OPU method
submit bio cache <---
blk_finish_plug <---
There are two issue:
1) for most of the time, 'submit bio cache' will break the merging in
current bio buffer from writes of next segments, making a smaller bio
submitting.
2) block plug only cover IO submitting in one segment, which reduce
opportunity of merging IOs in plug with multiple segments.
So refactor the code as below structure to strive for biggest
opportunity of merging IOs:
blk_start_plug
for each segment in victim section
for each valid block in segment
write out by OPU method
submit bio cache
blk_finish_plug
Test method:
1. mkfs.f2fs -s 8 /dev/sdX
2. touch 32 files
3. write 2M data into each file
4. punch 1.5M data from offset 0 for each file
5. trigger foreground gc through ioctl
Before patch, there are totoally 40 bios submitted.
f2fs_submit_write_bio: dev = (8,32), WRITE_SYNC, DATA, sector = 65536, size = 122880
f2fs_submit_write_bio: dev = (8,32), WRITE_SYNC, DATA, sector = 65776, size = 122880
f2fs_submit_write_bio: dev = (8,32), WRITE_SYNC, DATA, sector = 66016, size = 122880
f2fs_submit_write_bio: dev = (8,32), WRITE_SYNC, DATA, sector = 66256, size = 122880
f2fs_submit_write_bio: dev = (8,32), WRITE_SYNC, DATA, sector = 66496, size = 32768
----repeat for 8 times
After patch, there are totally 35 bios submitted.
f2fs_submit_write_bio: dev = (8,32), WRITE_SYNC, DATA, sector = 65536, size = 122880
----repeat 34 times
f2fs_submit_write_bio: dev = (8,32), WRITE_SYNC, DATA, sector = 73696, size = 16384
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
718e53fa63