[systemd-devel] Slow startup of systemd-journal on BTRFS

[Goffredo Baroncelli]

On 06/14/2014 04:03 PM, Kai Krakow wrote:
> Goffredo Baroncelli <kreijack at libero.it> schrieb:
> 
>> On 06/14/2014 12:59 PM, Kai Krakow wrote:
>> [...]
>>>
>>> I think that systemd is even one of the early supporters of btrfs because
>>> it will defragment readahead files on boot from btrfs.
>>
>> In know that systemd does readahead, but it is the first time that I heard
>> that it does defrag too. Could you elaborate ?
> 
> Look at src/readahead/readahead-collect.c. It works for btrfs and ext4. With 
> ext4 it will also relocate the files. Not sure if it does for btrfs. 

I am looking at the source, and yes, it does. To be honest it seems to defragment only on btrfs.

> If it 
> does, the question is: where to relocate in a multi devices file system?

Systemd uses the defrag capability of btrfs.

 
> That means, you have to enable systemd-readahead-collect, tho.
I have to admit that I disabled it. I will make some test also with readhead enabled. 


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