On Sun, May 03, 2015 at 12:02:08PM +0200, Toralf Förster wrote: > The picture in [1], created with isag from the sysstat package, shows > a periodic spike in the iowait of my tinderbox server (hardened Gentoo > 3.19.6-r1), correlating to write transactions per seconds from a > similar graph. > > I'm wondering what (kernel, btrfs or ?) is causing this.
Could be btrfs and the transaction commit, 30 seconds by default. The plot roughly matches to the ~30 seconds delay, but not everywhere. Raw numbers would could tell you more. Also, you could try to change the commit interval (mount option 'commit') and see if the iowait spikes change as well. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
