I have gotten what appear to be large increases in speed out of btrfs by
defragmentation of meta data. The manual defragmentation process takes
forever as you have to defragment incrementally directory by directory.
I was at the point where KDE startup times were getting abysmal (along
with journalctl, etc) and the multiple drives would churn incessantly on
startup. In the case of KDE, I found almost magical improvement with
one operation: `btrfs filesystem defrag /usr/share`. I am currently
going through the whole system deframenting directory by directory. Its
amazing, it proceeds quite quickly and then hits a directory at random
where it sits and plods away seemingly forever before moving on. I am
convinced that there is something going on here with meta data
fragmentation that, at times, is seriously affecting performance. I
*think* that autodefrag, once its out the door will hopefully solve
this, in the mean time I am trying to come up with some sort of way to
schedule an anacron job to deal with this issue. But my suggestion
would be that you try defragging your /var filesystem as thoroughly as
possible on the meta data side.
On 05/27/2013 09:21 AM, Szőts Ákos wrote:
Dear list,
I have two openSUSE 12.3 systems with kernel 3.9. On one of them there's an
ext4 partition, while on the other there's a btrfs.
I issued a "time journalctl -b --no-pager" command on both systems. This shows
the logs from the current boot without passing them to "less".
On ext4 (3.9.3):
real 0m1.898s
user 0m0.291s
sys 0m0.105s
On btrfs (3.9.2):
real 1m49.698s
user 0m0.102s
sys 0m0.470s
Journalctl on btrfs was always this slow, some btrfsck were made on the file
system too, but I don't think it was corrupted. On just the first run it's
sluggish, after it's fast as the ext4 one.
Is it a known issue or can I help somehow debugging this further?
Best regards,
Ákos Szőts
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