On Thu, Jun 12, 2014 at 11:21:04AM +1000, Dave Chinner wrote: > On Wed, Jun 11, 2014 at 11:28:54PM +0200, Goffredo Baroncelli wrote: > > Hi all, > > > > I would like to share a my experience about a slowness of systemd when used > > on BTRFS. > > > > My boot time was very high (about ~50 seconds); most of time it was due to > > NetworkManager which took about 30-40 seconds to start (this data came from > > "systemd-analyze plot"). > > > > I make several attempts to address this issue. Also I noticed that sometime > > this problem disappeared; but I was never able to understand why. > > > > However this link > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1006386 > > > > suggested me that the problem could be due to a bad interaction between > > systemd and btrfs. NetworkManager was innocent. > > systemd has a very stupid journal write pattern. It checks if there > is space in the file for the write, and if not it fallocates the > small amount of space it needs (it does *4 byte* fallocate calls!) > and then does the write to it. All this does is fragment the crap > out of the log files because the filesystems cannot optimise the > allocation patterns. > > Yup, it fragments journal files on XFS, too. > > http://oss.sgi.com/archives/xfs/2014-03/msg00322.html > > IIRC, the systemd developers consider this a filesystem problem and > so refused to change the systemd code to be nice to the filesystem > allocators, even though they don't actually need to use fallocate...
BTW, the systemd list is subscriber only, so thay aren't going to see anything that we comment on from a cross-post to the btrfs list. Cheers, Dave. -- Dave Chinner da...@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
