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

[Goffredo Baroncelli]

Hi Lennart,

On 06/16/2014 12:13 AM, Lennart Poettering wrote:
> I am not really following though why this trips up btrfs though. I am
> not sure I understand why this breaks btrfs COW behaviour. I mean,
> fallocate() isn't necessarily supposed to write anything really, it's
> mostly about allocating disk space in advance. I would claim that
> journald's usage of it is very much within the entire reason why it
> exists...

I performed several tests, trying different setups [1]. One of these was replacing the posix_fallocate() with a truncate, to check where is the problem. The conclusion was that *posix_fallocate() is NOT the problem*.

In another reply you stated that systemd-journald appends some data at the end of file, then update some data in the middle. I think this is the reason because the file becomes quickly fragmented.


[1] Let me to revise the english, the I will post the results.


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