[systemd-devel] udevadm settle takes too long to finish

[Thomas Bächler]

Am 07.12.2013 22:29, schrieb Robert Milasan:
> From systemd-analyze dump:
> 
>         Wants: systemd-udevd.service
>         WantedBy: lvm2-activation-early.service
>         WantedBy: lvm2-activation.service
>         Before: lvm2-activation-early.service
>         Before: sysinit.target
>         After: systemd-udev-trigger.service
>         After: systemd-journald.socket
>         References: systemd-udevd.service
>         References: systemd-udev-trigger.service
>         References: sysinit.target
>         References: systemd-journald.socket
>         ReferencedBy: lvm2-activation-early.service
>         ReferencedBy: lvm2-activation.service

What's the distribution you are using? Using udevadm settle for lvm is a
waste of boot time and isn't even guaranteed to work (ask Lennart, Kay
or Greg K-H for the full speech). It's a hackish workaround for LVM's
inability to activate volumes automatically.

Instead, a socket-activated lvmetad service should be used in
combination with the correct udev rules. The service files are provided
by LVM, but they reference weird redhat-specific units and from what I
saw have too many orderings, which results in slowing everything down
needlessly.

Currently, I use 69-dm-lvm-metad.rules provided by LVM in combination
with the unit files [1] and [2] (derived from the redhat units included
in LVM). This is fast and works great for me, although lvmetad has some
annoying bugs which have been reported to me, but which I could never
reproduce.

There is no way to make udevadm settle "faster" and the only solution is
(as Kay said already) is not using it.

[1]
https://projects.archlinux.org/svntogit/packages.git/tree/trunk/lvmetad.service?h=packages/lvm2
[2]
https://projects.archlinux.org/svntogit/packages.git/tree/trunk/lvmetad.socket?h=packages/lvm2

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