在通过 qemu 运行 NixOS 的 SystemD 系统上，我看到了此日志：
Aug 09 01:01:43 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:01 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:20 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:22 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:24 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:26 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:29 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:31 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:33 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:35 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:36 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:38 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:39 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:42 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:47 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:49 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:49 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:50 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:52 myhost systemd[1]: Looping too fast. Throttling execution a little.
Aug 09 01:02:53 myhost systemd[1]: Job basic.target/start timed out.
Aug 09 01:02:53 myhost systemd[1]: Timed out starting Basic System.
Aug 09 01:02:53 myhost systemd[1]: Dependency failed for Logrotate Service.
Aug 09 01:02:53 myhost systemd[1]: Dependency failed for Multi-User System.
Aug 09 01:02:53 myhost systemd[1]: Dependency failed for SCSI Link Power Management Policy.
Aug 09 01:02:53 myhost systemd[1]: Dependency failed for CPU Frequency Governor Setup.
Aug 09 01:02:53 myhost systemd[1]: Dependency failed for All Containers.
Aug 09 01:02:53 myhost systemd[1]: Dependency failed for Serial console liveness marker.
Aug 09 01:02:53 myhost systemd[1]: Forcibly powering off as result of failure.
Aug 09 01:02:53 myhost systemd[1]: Shutting down.
Aug 09 01:02:53 myhost nixos[18910]: switching to system configuration /nix/store/zfz756pkl9rsap4vh1frrs948k4lxvzn-nixos-1
Aug 09 01:02:53 myhost systemd-shutdown[1]: Sending SIGTERM to remaining processes…
（我删除了一些自定义单位的日志条目）
此后，虚拟机关闭。现在我想知道是什么导致了这种行为。