On Mon, Jan 2, 2017 at 2:02 PM, Jeff Mahoney <[email protected]> wrote:
> On 1/2/17 4:55 AM, Andrei Borzenkov wrote:
>> I try to understand what exactly is trimmed in case of btrfs. Using
>> installation in QEMU I see that host file size is about 9GB, allocated
>> size in guest approximately matches it and used space in guest is 7.6GB.
>> After some experimenting it looks like host size follows "Device
>> allocated" value in "btrfs filesystem usage" which leads me to believe
>> trim only considers space outside of allocated chunks. Is it correct?
>
> It should consider all available space. The code iterates over all
> block groups and trims free space and then iterates over free dev
> extents, which is all of the unallocated space.
>
> Which kernel version are you using? This stuff was broken for a while
> but was fixed in 4.3.
Appears for some time now, since I think 4.6 or 4.7, to only trim
unallocated space.
[chris@f25h ~]$ sudo btrfs fi us /
Overall:
Device size: 73.83GiB
Device allocated: 25.03GiB
Device unallocated: 48.80GiB
Device missing: 0.00B
Used: 21.29GiB
Free (estimated): 52.21GiB (min: 52.21GiB)
Data ratio: 1.00
Metadata ratio: 1.00
Global reserve: 71.16MiB (used: 0.00B)
Data,single: Size:24.00GiB, Used:20.59GiB
/dev/nvme0n1p4 20.00GiB
/dev/nvme0n1p6 4.00GiB
Metadata,single: Size:1.00GiB, Used:722.42MiB
/dev/nvme0n1p4 1.00GiB
System,single: Size:32.00MiB, Used:16.00KiB
/dev/nvme0n1p4 32.00MiB
Unallocated:
/dev/nvme0n1p4 3.97GiB
/dev/nvme0n1p6 44.83GiB
[chris@f25h ~]$ sudo fstrim -v /
[sudo] password for chris:
/: 48.8 GiB (52393148416 bytes) trimmed
[chris@f25h ~]$
Otherwise, it should have trimmed ~52GiB.
--
Chris Murphy
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