Excerpts from Bernhard Schmidt's message of 2011-05-03 07:30:36 -0400: > Am 03.05.2011 13:08, schrieb Chris Mason: > > >> defragging btrfs does not seem to work for me. I have run the filefrag > >> command over the whole fs and (manually) tried to defrag a few heavily > >> fragmented files, but I don't get it to work (it still has the same > >> number of extends and they are horrently uncorrelated) > >> > >> root@schleppi:~# filefrag > >> /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.4/cc1 > >> /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.4/cc1: 72 extents found > >> root@schleppi:~# btrfs filesystem defrag > >> /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.4/cc1 > >> root@schleppi:~# filefrag > >> /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.4/cc1 > >> /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.4/cc1: 72 extents found > >> > >> I'm using Ubuntu Natty (2.6.38.4) and tried both btrfs-tools from Natty > >> (201006xx) and from Debian experimental (git from 20101101). Both show > >> the same symptoms. I don't think fragmentation is bad on this box (due > >> to having an SSD), but my system at home is getting dog slow and I'd > >> like to try that when I come home end of the week. > > > > Do you have compression on? > > Yes. lzo to be exact. > > > The file the defrag ioctl works is that it schedules things for defrag > > but doesn't force out the IO immediately unless you use -f. > > > > So, to test the result of the defrag, you need to either wait a bit or > > run sync. > > Did so, no change. See my reply to cwillu for the data. > > I usually mount my / without any compression option and did "mount -o > remount,compress=lzo /" before. I cannot reboot at the moment and I did > not find any option to disable compression again. There does not seem to > be a "nocompress" or "compress=[none|off]" option. Is this correct?
Using compression is not a problem, but in order to reduce the maximum amount of ram we need to uncompress an extent, we enforce a max size on the extent. So you'll tend to have more extents, but they should be close together on disk. Could you please do a filefrag -v on the file? Lets see how bad it really is. -chris -- 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
