On Mon, Feb 11, 2013 at 2:34 AM, Gary van der Merwe <gary...@gmail.com> wrote: > Hi all. > > This is my first post to this list, so I just want to say I thank you > too all those > who wrote systemd. > > systemd-readahead-replay does not seem to be doing what it should. > > Bootchart with readahead-[replay|collect] enabled: > http://www.garyvdm.co.za/bootchart-20130211-1328.svg > > Output of `/usr/lib/systemd/systemd-readahead analyze /.readahead` : > http://www.garyvdm.co.za/systemd-readahead-analyze > > There is no output in `journalctl -u systemd-readahead-replay.service` > > Bootchart with readahead-[replay|collect] disabled: > http://www.garyvdm.co.za/bootchart-20130211-1409.svg > > Note that both my root & home partitions are btrfs with > options=defaults,noatime,compress=lzo. > > If you compare the bootcharts, you see that there is very little io reads when > systemd-readahead-replay starts. (Do systemd-readahead-replay reads not show > in > bootcharts by design?)
the replay thread should be relatively short-lived, and theoretically should run for about (readaheadvolume / hdd_speed) in time. > Am I correct in thinking that systemd-readahead-replay is not doing what it > should? absolutely. Or at least, something is preventing it from working properly. > How can I debug why it is not working? unfortunately, it's hard to debug this. I've attached strace -tt to -replay and get an idea of the timestamps of each fadvise() calls. Also, I see you're using btrfs. I've noticed bad btrfs performance with readahead and this reminds me that read_ahead_kb was horribly mistuned for btrfs - I think we included some fixes for it but I don't know whatever happened to those tunes. compression may also be an extra factor. what kind of drive does that system have? Cheers, Auke _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
