* btrfs fi defrag -c
@ 2011-10-27 19:20 Stephane Chazelas
2011-10-28 2:25 ` Li Zefan
2011-10-28 3:02 ` Li Zefan
0 siblings, 2 replies; 4+ messages in thread
From: Stephane Chazelas @ 2011-10-27 19:20 UTC (permalink / raw)
To: linux-btrfs
I don't quite understand the behavior of "btrfs fi defrag"
~# truncate -s2G ~/a
~# mkfs.btrfs ~/a
nodesize 4096 leafsize 4096 sectorsize 4096 size 2.00GB
~# mount -o loop ~/a /mnt/1
/mnt/1# cd x
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 64K 1.8G 1% /mnt/1
/mnt/1# yes | head -c400M > a
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 64K 1.8G 1% /mnt/1
/mnt/1# sync
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 402M 1.4G 23% /mnt/1
/mnt/1# btrfs fi defrag -c a
(exit status == 20 BTW).
(20)/mnt/1# sync
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 415M 994M 30% /mnt/1
No space gain, even lost 15M or 400M depending on how you look at it.
/mnt/1# btrfs fi defrag a
(20)/mnt/1# sync
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 797M 612M 57% /mnt/1
Lost another 400M.
/mnt/1# ls -l
total 409600
-rw-r--r-- 1 root root 419430400 Oct 27 19:53 a
/mnt/1# btrfs fi balance .
/mnt/1# sync
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 798M 845M 49% /mnt/1
Possibly reclaimed some of the space?
At the point where it says 612M free, if I do:
/mnt/1# cat < /dev/zero > b
cat: write error: No space left on device
/mnt/1# ls -lh b
-rw-r--r-- 1 root root 612M Oct 27 20:14 b
There was indeed 612M free.
When the FS is mounted with compress:
~# mkfs.btrfs ./a
nodesize 4096 leafsize 4096 sectorsize 4096 size 2.00GB
~# mount -o compress ./a /mnt/1
~# cd /mnt/1
/mnt/1# yes | head -c400M > a
/mnt/1# sync
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 14M 1.8G 1% /mnt/1
/mnt/1# btrfs fi defrag -c ./a
(20)/mnt/1# sync
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 21M 1.4G 2% /mnt/1
Lost 400M?
/mnt/1# btrfs fi defrag ./a
(20)/mnt/1# sync
/mnt/1# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/loop1 2.0G 21M 1.4G 2% /mnt/1
I take it it doesn't uncompress?
I'm a bit confused here.
(that's with 3.0 amd64)
--
Stephane
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: btrfs fi defrag -c
2011-10-27 19:20 btrfs fi defrag -c Stephane Chazelas
@ 2011-10-28 2:25 ` Li Zefan
2011-10-28 10:23 ` Stephane CHAZELAS
2011-10-28 3:02 ` Li Zefan
1 sibling, 1 reply; 4+ messages in thread
From: Li Zefan @ 2011-10-28 2:25 UTC (permalink / raw)
To: Stephane Chazelas; +Cc: linux-btrfs
Stephane Chazelas wrote:
> I don't quite understand the behavior of "btrfs fi defrag"
>
> ~# truncate -s2G ~/a
> ~# mkfs.btrfs ~/a
> nodesize 4096 leafsize 4096 sectorsize 4096 size 2.00GB
> ~# mount -o loop ~/a /mnt/1
> /mnt/1# cd x
> /mnt/1# df -h .
> Filesystem Size Used Avail Use% Mounted on
> /dev/loop1 2.0G 64K 1.8G 1% /mnt/1
> /mnt/1# yes | head -c400M > a
> /mnt/1# df -h .
> Filesystem Size Used Avail Use% Mounted on
> /dev/loop1 2.0G 64K 1.8G 1% /mnt/1
> /mnt/1# sync
> /mnt/1# df -h .
> Filesystem Size Used Avail Use% Mounted on
> /dev/loop1 2.0G 402M 1.4G 23% /mnt/1
> /mnt/1# btrfs fi defrag -c a
>
> (exit status == 20 BTW).
>
int do_defrag(int ac, char **av)
{
...
return errors + 20;
}
This doesn't make sense to me.
> (20)/mnt/1# sync
> /mnt/1# df -h .
> Filesystem Size Used Avail Use% Mounted on
> /dev/loop1 2.0G 415M 994M 30% /mnt/1
>
> No space gain, even lost 15M or 400M depending on how you look at it.
>
Here's mine:
# df . -h
Filesystem Size Used Avail Use% Mounted on
/home/lizf/tmp/a 2.0G 409M 1.4G 23% /mnt
And I was not suprised, as there's a regression.
With this fix:
http://marc.info/?l=linux-btrfs&m=131495014823121&w=2
# df . -h
Filesystem Size Used Avail Use% Mounted on
/home/lizf/tmp/a 2.0G 14M 1.8G 1% /mnt
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: btrfs fi defrag -c
2011-10-27 19:20 btrfs fi defrag -c Stephane Chazelas
2011-10-28 2:25 ` Li Zefan
@ 2011-10-28 3:02 ` Li Zefan
1 sibling, 0 replies; 4+ messages in thread
From: Li Zefan @ 2011-10-28 3:02 UTC (permalink / raw)
To: Stephane Chazelas; +Cc: linux-btrfs
> When the FS is mounted with compress:
>
> ~# mkfs.btrfs ./a
> nodesize 4096 leafsize 4096 sectorsize 4096 size 2.00GB
> ~# mount -o compress ./a /mnt/1
> ~# cd /mnt/1
> /mnt/1# yes | head -c400M > a
> /mnt/1# sync
> /mnt/1# df -h .
> Filesystem Size Used Avail Use% Mounted on
> /dev/loop1 2.0G 14M 1.8G 1% /mnt/1
> /mnt/1# btrfs fi defrag -c ./a
> (20)/mnt/1# sync
> /mnt/1# df -h .
> Filesystem Size Used Avail Use% Mounted on
> /dev/loop1 2.0G 21M 1.4G 2% /mnt/1
>
> Lost 400M?
>
> /mnt/1# btrfs fi defrag ./a
> (20)/mnt/1# sync
> /mnt/1# df -h .
> Filesystem Size Used Avail Use% Mounted on
> /dev/loop1 2.0G 21M 1.4G 2% /mnt/1
>
> I take it it doesn't uncompress?
>
> I'm a bit confused here.
>
Yes, it won't be uncompressed if you mount with compress option.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: btrfs fi defrag -c
2011-10-28 2:25 ` Li Zefan
@ 2011-10-28 10:23 ` Stephane CHAZELAS
0 siblings, 0 replies; 4+ messages in thread
From: Stephane CHAZELAS @ 2011-10-28 10:23 UTC (permalink / raw)
To: linux-btrfs
2011-10-28, 10:25(+08), Li Zefan:
[...]
> # df . -h
> Filesystem Size Used Avail Use% Mounted on
> /home/lizf/tmp/a 2.0G 409M 1.4G 23% /mnt
OK, why are we not gaining space after compression though?
> And I was not suprised, as there's a regression.
>
> With this fix:
>
> http://marc.info/?l=linux-btrfs&m=131495014823121&w=2
[...]
Thanks. That's the one that's scheduled for 3.2 and maybe 3.1.x,
right?
--
Stephane
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2011-10-28 10:23 UTC | newest]
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2011-10-27 19:20 btrfs fi defrag -c Stephane Chazelas
2011-10-28 2:25 ` Li Zefan
2011-10-28 10:23 ` Stephane CHAZELAS
2011-10-28 3:02 ` Li Zefan
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