Startup finished in 5min 11.381s (kernel) + 17.186s (userspace) = 5min 28.568s
graphical.target reached after 17.159s in userspace
服务加载速度很快，但无法弄清楚为什么内核需要 5 分钟以上的时间才能启动。该机器有 24 个内核、64GB RAM 和快速 CPU。在哪里可以找到内核耗时这么长的原因？
dmesg仅显示 UFW 块。syslog偶尔显示此行
ubuntu kernel: [141881.865777] perf: interrupt took too long (5083 > 4933), lowering kernel.perf_event_max_sample_rate to 39250
/etc/fstab
# <file system> <mount point> <type> <options> <dump> <pass>
# / was on /dev/sda3 during installation
UUID=806f2d97-f0bc-4468-97c8-faca9c935380 / ext4 errors=remount-ro 0 1
# /boot was on /dev/sda1 during installation
UUID=70f9615c-accc-4a91-8fa8-c8482972fb48 /boot ext4 defaults 0 2
# /mnt/md0 was on /dev/md0 during installation
UUID=dffbeccd-a777-40f5-8e56-756366ab198f /mnt/md0 ext4 defaults 0 2
# swap was on /dev/sda2 during installation
UUID=63dc9015-84ad-4dbb-a0d9-e3a6653f4e70 none swap sw 0 0
更新：删除了交换但没有什么区别
更新：KVM 无法访问服务器。托管服务提供商重新启动了 KVM。之后，Ubuntu 服务器在 15 秒内开始启动。可能是允许访问服务器的 KVM 冻结导致了启动缓慢的问题。