There is some angles of attack here:
└─zfs-import-cache.service @1min 786ms +272ms
└─systemd-udev-settle.service @494ms +1min 275ms
This is a case of "you asked for it, you got it", really. udev-settle is
a workaround for old software that wasn't written with hotplugging in
mind. It's 2016, and we really should avoid introducing new dependencies
to udev-settle, as it's conceptually broken and can't work. This
totally does not work for any hotplugged device, or a device which just
gets detected by the kernel late, or which needs to be unwrapped from
building an LVM or cryptsetup device, etc.
I think it would be much more elegant to instead create udev rules (or
systemd units) which load the ZFS cache as soon as a ZFS block device is
detected. Would that be possible/reasonable? I don't know anything about
what import-cache does, but I hope/suppose it has some way of doing this
on a per-device basis?
└─systemd-udev-trigger.service @415ms +55ms
This is cloud-init's rules for blocking udev rules until network devices
get detected and cloud-init's naming rules get applied. This is a hairy
topic and Scott and I already discussed this at length. I think there's
a better solution here, but I doubt we'll completely turn this around by
the release. This just illustrates one of the problems of the "waiting
for all hardware just to single out a particular device" approach from
above -- this waits on stuff which is completely unrelated to zfs.
** No longer affects: systemd (Ubuntu)
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https://bugs.launchpad.net/bugs/1571761
Title:
zfs-import-cache.service slows boot by 60 seconds
Status in cloud-init package in Ubuntu:
Confirmed
Status in zfs-linux package in Ubuntu:
Confirmed
Bug description:
Fresh uvt-kvm guest, then
$ sudo apt-get install zfsutils-linux
$ sudo reboot
The reboot will show on console waiting for tasks, then after ~ 60 seconds it
continues boot.
Logging in shows:
$ sudo systemd-analyze critical-chain zfs-mount.service
The time after the unit is active or started is printed after the "@"
character.
The time the unit takes to start is printed after the "+" character.
zfs-mount.service +81ms
└─zfs-import-cache.service @1min 786ms +272ms
└─systemd-udev-settle.service @494ms +1min 275ms
└─systemd-udev-trigger.service @415ms +55ms
└─systemd-udevd-control.socket @260ms
└─-.mount @124ms
└─system.slice @129ms
└─-.slice @124ms
Seems possibly related / or some discussion at
https://github.com/zfsonlinux/zfs/issues/2368
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: zfsutils-linux 0.6.5.6-0ubuntu8
ProcVersionSignature: User Name 4.4.0-18.34-generic 4.4.6
Uname: Linux 4.4.0-18-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.20.1-0ubuntu1
Architecture: amd64
Date: Mon Apr 18 16:42:35 2016
ProcEnviron:
TERM=screen.xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: zfs-linux
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.sudoers.d.zfs: [deleted]
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