Am Mon, 10 Apr 2017 13:13:39 -0400 schrieb "Austin S. Hemmelgarn" <ahferroin7@xxxxxxxxx>: > On 2017-04-10 12:54, Kai Krakow wrote: > > Am Mon, 10 Apr 2017 18:44:44 +0200 > > schrieb Kai Krakow <hurikhan77@xxxxxxxxx>: > > > >> Am Mon, 10 Apr 2017 08:51:38 -0400 > >> schrieb "Austin S. Hemmelgarn" <ahferroin7@xxxxxxxxx>: > >> > [...] > [...] > >> [...] > [...] > [...] > >> > >> Did you put it in /etc/fstab only for the rootfs? If yes, it > >> probably has no effect. You would need to give it as rootflags on > >> the kernel cmdline. > > > > I did a "fgrep lazytime /usr/src/linux -ir" and it reveals only ext4 > > and f2fs know the flag. Kernel 4.10. > > > > So probably you're seeing a placebo effect. If you put lazytime for > > rootfs just only into fstab, it won't have an effect because on > > initial mount this file cannot be opened (for obvious reasons), and > > on remount, btrfs seems to happily accept lazytime but it has no > > effect. It won't show up in /proc/mounts. Try using it in rootflags > > kernel cmdline and you should see that the kernel won't accept the > > flag lazytime. > The command-line also rejects a number of perfectly legitimate > arguments that BTRFS does understand too though, so that's not much > of a test. Which are those? I didn't encounter any... > I've just finished some quick testing though, and it looks > like you're right, BTRFS does not support this, which means I now > need to figure out what the hell was causing the IOPS counters in > collectd to change in rough correlation with remounting (especially > since it appears to happen mostly independent of the options being > changed). I think that noatime (which I remember you also used?), lazytime, and relatime are mutually exclusive: they all handle the inode updates. Maybe that is the effect you see? > This is somewhat disappointing though, as supporting this would > probably help with the write-amplification issues inherent in COW > filesystems. -- Well, relatime is mostly the same thus not perfectly resembling the POSIX standard. I think the only software that relies on atime is mutt... -- Regards, Kai Replies to list-only preferred. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
