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

[Martin]

On 16/06/14 19:47, Goffredo Baroncelli wrote:
> Hi all,
> 
> in this blog [1] I collected all the results of the tests which I
> performed in order to investigate a bit this performance problem
> between systemd and btrfs. I had to put these results in a blog,
> because there are several images. Below a brief summary.

> The test #1 highlight the problem. It shows that the boot time may
> require up to 50 seconds. During the reboots the number of extents of
> the file system.journal increases up to 6000. De-fragmenting the
> system.journal file the boot time decreases by ~20 seconds. My
> conclusion is that in BTRFS the fragmentation of this file increases
> the boot time.
> 
> The test #6 and #7 suggested that the fsync(2) amd posix_fallocate(3)
> calls aren't the root cause of the problem. Even without these the
> system.journal file still fragments.


> [1]
> http://kreijack.blogspot.it/2014/06/btrfs-and-systemd-journal.html

Very good demonstration and summary, thanks.

The charts very clearly show the correspondence between time-to-boot and
the level of fragmentation.

... And I thought Linux was getting ever faster to boot!


Regards,
Martin