我使用的是 SSD，文件碎片本来就不是什么大问题，但我注意到 grub 中的“正在加载初始 ramdisk...”消息比我认为的要长。它持续了大约 7 秒钟，然后 Plymouth 才开始运行。Plymouth 本身只需要大约 3 秒钟（不过，如果它能更早启动并持续更长时间就好了）。然后 lightdm/greeter 屏幕会在 2 到 3 秒内出现。
因此我做了一些实验并运行filefrag -v /boot/init*后发现我的内核 4.4.0-53 似乎过于碎片化：
File size of /boot/initrd.img-4.4.0-53-generic is 49027703 (11970 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 3: 4351562.. 4351565: 4:
1: 4.. 4095: 2334720.. 2338811: 4092: 4351566:
2: 4096.. 8191: 2330624.. 2334719: 4096: 2338812:
3: 8192.. 10239: 2355200.. 2357247: 2048: 2334720:
4: 10240.. 11969: 2408448.. 2410177: 1730: 2357248: last,eof
我很好奇碎片化initrd.img会如何影响启动性能。碎片整理值得吗？
initrd.img当然，我也始终乐于接受有关使其变得更小、更快的建议。
笔记：除了 mSata SSD 和全尺寸 SSD，我的笔记本电脑还配备了一个全尺寸 HDD，其中包含 Ubuntu 14.04，因此我对碎片整理很感兴趣initrd.img，而不仅仅是 SSD。当前的启动会话来自 mSata SSD，但它的速度限制为 SATA II，而全尺寸驱动器的速度则位于 SATA III 总线上。
编辑 1：-systemd启动图表
根据以下评论，我添加了systemd-bootchart它是通过修改 grub 内核参数生成的：
GRUB_CMDLINE_LINUX_DEFAULT="splash vt.handoff=7 kaslr init=/lib/systemd/systemd-bootchart"
启动图表保存到：/run/log/bootchart-20161224-1801.svg。我不得不使用以 75% 质量gimp的格式打开并导出它，.jpg以使其符合 Ask Ubuntu 的 2.1 MB 限制。导出的文件如下所示：
注意开始时的 9 秒延迟。grub 中“正在加载初始 ramdisk ...”消息的“正常”延迟为 7 秒，现在约为 10 秒。额外的时间可能归因于systemd-bootchart高架。
编辑 2：RAM 和 cgroups
按照下面的评论（请求）RAM并cgroups包含/var/log/syslog在此编辑中。
输出自free -m：
$ free -m
total used free shared buff/cache available
Mem: 7843 3167 820 1574 3854 2740
Swap: 7999 4 7995
请注意，SWAP 仅用于测试OOM Killer，可以擦除。实际上，从技术上讲，它本来就不应该位于 SSD 上。
输出自grep cgroup < /var/log/syslog.1：
$ grep cgroup < /var/log/syslog.1
Dec 24 15:22:50 dell kernel: [ 0.000000] Initializing cgroup subsys cpuset
Dec 24 15:22:50 dell kernel: [ 0.000000] Initializing cgroup subsys cpu
Dec 24 15:22:50 dell kernel: [ 0.000000] Initializing cgroup subsys cpuacct
Dec 24 15:22:50 dell kernel: [ 0.011642] Initializing cgroup subsys io
Dec 24 15:22:50 dell kernel: [ 0.011645] Initializing cgroup subsys memory
Dec 24 15:22:50 dell kernel: [ 0.011651] Initializing cgroup subsys devices
Dec 24 15:22:50 dell kernel: [ 0.011653] Initializing cgroup subsys freezer
Dec 24 15:22:50 dell kernel: [ 0.011655] Initializing cgroup subsys net_cls
Dec 24 15:22:50 dell kernel: [ 0.011657] Initializing cgroup subsys perf_event
Dec 24 15:22:50 dell kernel: [ 0.011659] Initializing cgroup subsys net_prio
Dec 24 15:22:50 dell kernel: [ 0.011662] Initializing cgroup subsys hugetlb
Dec 24 15:22:50 dell kernel: [ 0.011664] Initializing cgroup subsys pids
Dec 24 15:22:50 dell kernel: [ 6.204710] cgroup: new mount options do not match the existing superblock, will be ignored
Dec 24 15:23:33 dell kernel: [ 0.000000] Initializing cgroup subsys cpuset
Dec 24 15:23:33 dell kernel: [ 0.000000] Initializing cgroup subsys cpu
Dec 24 15:23:33 dell kernel: [ 0.000000] Initializing cgroup subsys cpuacct
Dec 24 15:23:33 dell kernel: [ 0.010846] Initializing cgroup subsys io
Dec 24 15:23:33 dell kernel: [ 0.010849] Initializing cgroup subsys memory
Dec 24 15:23:33 dell kernel: [ 0.010855] Initializing cgroup subsys devices
Dec 24 15:23:33 dell kernel: [ 0.010857] Initializing cgroup subsys freezer
Dec 24 15:23:33 dell kernel: [ 0.010860] Initializing cgroup subsys net_cls
Dec 24 15:23:33 dell kernel: [ 0.010861] Initializing cgroup subsys perf_event
Dec 24 15:23:33 dell kernel: [ 0.010864] Initializing cgroup subsys net_prio
Dec 24 15:23:33 dell kernel: [ 0.010867] Initializing cgroup subsys hugetlb
Dec 24 15:23:33 dell kernel: [ 0.010868] Initializing cgroup subsys pids
Dec 24 15:23:33 dell kernel: [ 7.338815] cgroup: new mount options do not match the existing superblock, will be ignored
Dec 24 15:45:25 dell kernel: [ 0.000000] Initializing cgroup subsys cpuset
Dec 24 15:45:25 dell kernel: [ 0.000000] Initializing cgroup subsys cpu
Dec 24 15:45:25 dell kernel: [ 0.000000] Initializing cgroup subsys cpuacct
Dec 24 15:45:25 dell kernel: [ 0.010844] Initializing cgroup subsys io
Dec 24 15:45:25 dell kernel: [ 0.010847] Initializing cgroup subsys memory
Dec 24 15:45:25 dell kernel: [ 0.010853] Initializing cgroup subsys devices
Dec 24 15:45:25 dell kernel: [ 0.010855] Initializing cgroup subsys freezer
Dec 24 15:45:25 dell kernel: [ 0.010857] Initializing cgroup subsys net_cls
Dec 24 15:45:25 dell kernel: [ 0.010859] Initializing cgroup subsys perf_event
Dec 24 15:45:25 dell kernel: [ 0.010861] Initializing cgroup subsys net_prio
Dec 24 15:45:25 dell kernel: [ 0.010864] Initializing cgroup subsys hugetlb
Dec 24 15:45:25 dell kernel: [ 0.010866] Initializing cgroup subsys pids
Dec 24 15:45:25 dell kernel: [ 5.977461] cgroup: new mount options do not match the existing superblock, will be ignored
Dec 24 16:09:31 dell kernel: [ 0.000000] Initializing cgroup subsys cpuset
Dec 24 16:09:31 dell kernel: [ 0.000000] Initializing cgroup subsys cpu
Dec 24 16:09:31 dell kernel: [ 0.000000] Initializing cgroup subsys cpuacct
Dec 24 16:09:31 dell kernel: [ 0.010848] Initializing cgroup subsys io
Dec 24 16:09:31 dell kernel: [ 0.010852] Initializing cgroup subsys memory
Dec 24 16:09:31 dell kernel: [ 0.010858] Initializing cgroup subsys devices
Dec 24 16:09:31 dell kernel: [ 0.010860] Initializing cgroup subsys freezer
Dec 24 16:09:31 dell kernel: [ 0.010862] Initializing cgroup subsys net_cls
Dec 24 16:09:31 dell kernel: [ 0.010864] Initializing cgroup subsys perf_event
Dec 24 16:09:31 dell kernel: [ 0.010866] Initializing cgroup subsys net_prio
Dec 24 16:09:31 dell kernel: [ 0.010870] Initializing cgroup subsys hugetlb
Dec 24 16:09:31 dell kernel: [ 0.010871] Initializing cgroup subsys pids
Dec 24 16:09:31 dell kernel: [ 6.663158] cgroup: new mount options do not match the existing superblock, will be ignored
Dec 24 18:00:44 dell kernel: [ 0.000000] Initializing cgroup subsys cpuset
Dec 24 18:00:44 dell kernel: [ 0.000000] Initializing cgroup subsys cpu
Dec 24 18:00:44 dell kernel: [ 0.000000] Initializing cgroup subsys cpuacct
Dec 24 18:00:44 dell kernel: [ 0.011644] Initializing cgroup subsys io
Dec 24 18:00:44 dell kernel: [ 0.011647] Initializing cgroup subsys memory
Dec 24 18:00:44 dell kernel: [ 0.011654] Initializing cgroup subsys devices
Dec 24 18:00:44 dell kernel: [ 0.011656] Initializing cgroup subsys freezer
Dec 24 18:00:44 dell kernel: [ 0.011658] Initializing cgroup subsys net_cls
Dec 24 18:00:44 dell kernel: [ 0.011660] Initializing cgroup subsys perf_event
Dec 24 18:00:44 dell kernel: [ 0.011662] Initializing cgroup subsys net_prio
Dec 24 18:00:44 dell kernel: [ 0.011665] Initializing cgroup subsys hugetlb
Dec 24 18:00:44 dell kernel: [ 0.011667] Initializing cgroup subsys pids
Dec 24 18:00:44 dell kernel: [ 6.388658] cgroup: new mount options do not match the existing superblock, will be ignored
Dec 24 18:01:33 dell kernel: [ 0.000000] Initializing cgroup subsys cpuset
Dec 24 18:01:33 dell kernel: [ 0.000000] Initializing cgroup subsys cpu
Dec 24 18:01:33 dell kernel: [ 0.000000] Initializing cgroup subsys cpuacct
Dec 24 18:01:33 dell kernel: [ 0.010850] Initializing cgroup subsys io
Dec 24 18:01:33 dell kernel: [ 0.010854] Initializing cgroup subsys memory
Dec 24 18:01:33 dell kernel: [ 0.010860] Initializing cgroup subsys devices
Dec 24 18:01:33 dell kernel: [ 0.010862] Initializing cgroup subsys freezer
Dec 24 18:01:33 dell kernel: [ 0.010864] Initializing cgroup subsys net_cls
Dec 24 18:01:33 dell kernel: [ 0.010866] Initializing cgroup subsys perf_event
Dec 24 18:01:33 dell kernel: [ 0.010868] Initializing cgroup subsys net_prio
Dec 24 18:01:33 dell kernel: [ 0.010871] Initializing cgroup subsys hugetlb
Dec 24 18:01:33 dell kernel: [ 0.010873] Initializing cgroup subsys pids
Dec 24 18:01:34 dell kernel: [ 12.036550] cgroup: new mount options do not match the existing superblock, will be ignored
请注意，该日志包含多次启动。
编辑 3-速度提高。
在实施问答答案之后，我写道（如何为‘rm’命令设置密码？) 其中包装脚本密码保护rm命令，启动速度提高了一倍。
这是新图表：
答案1
我不认为碎片整理是你的问题，但你可以这样做......
在terminal...
输入
man update-initramfs#来了解有关此命令的更多信息。然后输入
sudo update-initramfs -c#从头创建一个新文件。然后输入
reboot