从内核 4.5 开始，启动时间从 900 毫秒 (4.4.44) 增加到 2.1 秒 (4.9.5)。
我想修复，或者至少通过打开适当的错误报告来帮助开发人员，但我不知道提供哪些信息来填写有用的报告。
那么，如何调查这个内核启动时问题呢？
聚苯乙烯：我使用的是带有 Arch Linux x86_64 和 Gnome 的 Dell XPS 9343 (Broadwell)。
PS2：实际上我的系统中安装了 LTS 内核 (4.4.44) 和 -ck (4.9.5)，我从 systemd-boot 菜单中选择它们，上面报告的时间是从命令中获取的systemd-analyze，核心入口。
PS3：当我注意到（并测量）启动时间增加时，我注意到关机时也有同样的情况，但在这种情况下我不知道如何测量它。
编辑1：请求内核 4.9 的输出
[mattia@arch-xps ~]$ systemd-analyze blame
2.356s dev-sda3.device
1.648s systemd-fsck@dev-disk-by\x2duuid-88E7\x2d8ACB.service
1.646s systemd-fsck@dev-disk-by\x2duuid-e2a87acb\x2d9e12\x2d4501\x2dbb
1.346s tlp.service
1.324s systemd-journald.service
1.307s systemd-udev-trigger.service
1.306s systemd-tmpfiles-setup-dev.service
1.296s colord.service
1.005s systemd-journal-flush.service
947ms [email protected]
944ms systemd-timesyncd.service
854ms accounts-daemon.service
564ms systemd-rfkill.service
244ms org.cups.cupsd.service
163ms packagekit.service
89ms NetworkManager.service
86ms bluetooth.service
75ms systemd-logind.service
53ms upower.service
53ms [email protected]
49ms polkit.service
43ms systemd-udevd.service
38ms wpa_supplicant.service
36ms udisks2.service
28ms systemd-sysctl.service
25ms systemd-tmpfiles-clean.service
22ms boot.mount
20ms systemd-random-seed.service
19ms gdm.service
16ms geoclue.service
16ms systemd-backlight@leds:dell::kbd_backlight.service
14ms kmod-static-nodes.service
13ms systemd-remount-fs.service
11ms dev-sda2.swap
11ms dev-mqueue.mount
10ms systemd-tmpfiles-setup.service
10ms sys-kernel-debug.mount
8ms systemd-backlight@backlight:intel_backlight.service
7ms home.mount
6ms systemd-update-utmp.service
6ms sys-kernel-config.mount
6ms systemd-user-sessions.service
5ms dev-hugepages.mount
5ms rtkit-daemon.service
3ms sys-fs-fuse-connections.mount
3ms tmp.mount
[mattia@arch-xps ~]$ systemd-analyze critical-chain
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.
graphical.target @5.282s
└─gdm.service @5.258s +19ms
└─systemd-user-sessions.service @5.244s +6ms
└─nss-user-lookup.target @5.288s
编辑2：请求内核 4.4 的输出
[mattia@arch-xps ~]$ systemd-analyze blame
1.356s systemd-fsck@dev-disk-by\x2duuid-e2a87acb\x2d9e12\x2d4501\x2dbb
1.355s systemd-rfkill.service
895ms [email protected]
861ms tlp.service
474ms dev-sda3.device
379ms systemd-localed.service
310ms systemd-hostnamed.service
310ms systemd-timedated.service
255ms systemd-timesyncd.service
188ms org.cups.cupsd.service
146ms systemd-journald.service
112ms packagekit.service
60ms bluetooth.service
60ms NetworkManager.service
59ms accounts-daemon.service
58ms upower.service
49ms systemd-udevd.service
48ms systemd-fsck@dev-disk-by\x2duuid-88E7\x2d8ACB.service
37ms [email protected]
36ms polkit.service
33ms systemd-udev-trigger.service
25ms systemd-journal-flush.service
24ms systemd-tmpfiles-setup-dev.service
22ms udisks2.service
17ms gdm.service
16ms kmod-static-nodes.service
16ms dev-sda2.swap
16ms boot.mount
15ms colord.service
15ms sys-kernel-debug.mount
13ms systemd-remount-fs.service
13ms dev-hugepages.mount
13ms geoclue.service
13ms systemd-sysctl.service
13ms home.mount
10ms systemd-logind.service
9ms sys-kernel-config.mount
8ms wpa_supplicant.service
8ms systemd-tmpfiles-setup.service
7ms systemd-random-seed.service
7ms systemd-backlight@leds:dell::kbd_backlight.service
5ms systemd-update-utmp.service
5ms rtkit-daemon.service
4ms systemd-user-sessions.service
4ms tmp.mount
3ms systemd-backlight@backlight:intel_backlight.service
3ms dev-mqueue.mount
2ms sys-fs-fuse-connections.mount
[mattia@arch-xps ~]$ systemd-analyze critical-chain
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.
graphical.target @2.555s
└─gdm.service @2.536s +17ms
└─systemd-user-sessions.service @2.525s +4ms
└─nss-user-lookup.target @2.559s
编辑3：不，它们的尺寸大约相同。
[mattia@arch-xps ~]$ ls /boot/
total 62M
drwxr-xr-x 5 root root 4.0K Jan 1 1970 .
drwxr-xr-x 17 root root 4.0K Dec 10 17:31 ..
drwxr-xr-x 6 root root 4.0K Dec 14 17:49 EFI
drwxr-xr-x 2 root root 4.0K Jan 11 16:39 grub
drwxr-xr-x 3 root root 4.0K May 14 2016 loader
-rwxr-xr-x 1 root root 21M Jan 20 15:40 initramfs-linux-ck-fallback.img
-rwxr-xr-x 1 root root 5.7M Jan 20 15:40 initramfs-linux-ck.img
-rwxr-xr-x 1 root root 20M Jan 17 18:01 initramfs-linux-lts-fallback.img
-rwxr-xr-x 1 root root 5.6M Jan 17 18:01 initramfs-linux-lts.img
-rwxr-xr-x 1 root root 961K Nov 15 18:43 intel-ucode.img
-rwxr-xr-x 1 root root 4.6M Jan 20 15:38 vmlinuz-linux-ck
-rwxr-xr-x 1 root root 4.3M Jan 15 15:05 vmlinuz-linux-lts
编辑4：尝试使用官方存储库中的内核（请参阅第六条第七条评论），启动时间显着不同，为 1.3 秒，但仍然高于内核 4.4
[mattia@arch-xps ~]$ systemd-analyze blame
1.979s dev-sda3.device
1.369s systemd-journald.service
1.347s colord.service
871ms systemd-udev-trigger.service
868ms [email protected]
868ms systemd-tmpfiles-setup-dev.service
793ms systemd-udevd.service
782ms tlp.service
508ms systemd-timesyncd.service
503ms [email protected]
473ms wpa_supplicant.service
177ms org.cups.cupsd.service
110ms packagekit.service
85ms NetworkManager.service
85ms systemd-journal-flush.service
66ms systemd-fsck@dev-disk-by\x2duuid-e2a87acb\x2d9e12\x2d4501\x2dbb
49ms upower.service
47ms systemd-fsck@dev-disk-by\x2duuid-88E7\x2d8ACB.service
44ms accounts-daemon.service
28ms bluetooth.service
27ms polkit.service
24ms gdm.service
22ms udisks2.service
18ms systemd-rfkill.service
16ms systemd-logind.service
15ms geoclue.service
13ms boot.mount
13ms dev-hugepages.mount
12ms dev-mqueue.mount
11ms systemd-remount-fs.service
11ms systemd-backlight@leds:dell::kbd_backlight.service
11ms systemd-sysctl.service
10ms sys-kernel-config.mount
9ms dev-sda2.swap
9ms kmod-static-nodes.service
8ms systemd-user-sessions.service
7ms home.mount
7ms systemd-backlight@backlight:intel_backlight.service
7ms systemd-tmpfiles-setup.service
6ms systemd-update-utmp.service
5ms tmp.mount
5ms systemd-random-seed.service
4ms rtkit-daemon.service
4ms sys-fs-fuse-connections.mount
2ms sys-kernel-debug.mount
[mattia@arch-xps ~]$ systemd-analyze critical-chain
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.
graphical.target @4.604s
└─gdm.service @4.397s +24ms
└─systemd-user-sessions.service @4.379s +8ms
└─nss-user-lookup.target @4.425s