On Sun, Nov 19, 2017 at 7:13 PM, Qu Wenruo <quwenruo.btrfs@xxxxxxx> wrote:
>
>
> On 2017年11月19日 14:17, Chris Murphy wrote:
>> fstrim should trim free space, but it only trims unallocated. This is
>> with kernel 4.14.0 and the entire 4.13 series. I'm pretty sure it
>> behaved this way with 4.12 also.
>
> Tested with 4.14-rc7, can't reproduce it.
$ sudo btrfs fi us /
Overall:
Device size: 70.00GiB
Device allocated: 31.03GiB
Device unallocated: 38.97GiB
Device missing: 0.00B
Used: 22.12GiB
Free (estimated): 47.62GiB (min: 47.62GiB)
...snip...
$ sudo fstrim -v /
/: 39 GiB (41841328128 bytes) trimmed
Then I run btrfs-debug -b / and find the least used block group, at 8% usage;
block group offset 174202028032 len 1073741824 used 89206784
chunk_objectid 256 flags 1 usage 0.08
And balance that block group:
$ sudo btrfs balance start -dvrange=174202028032..174202028033 -dlimit=1 /
Done, had to relocate 1 out of 32 chunks
And trim again:
/: 39 GiB (41841328128 bytes) trimmed
> Any special mount options or setup?
> (BTW, I also tried space_cache=v2 and default v1, no obvious difference)
/dev/nvme0n1p8 on / type btrfs
(rw,relatime,seclabel,ssd,space_cache,subvolid=333,subvol=/root27)
Would a strace of fstrim help?
--
Chris Murphy
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