This is probably unanswerable. But maybe someone else will have this problem and find this question, append to it, or proffer an answer.

I discovered the pidstat command with its -d option, today. Apparently, on my RHEL6 systems, init (upstart) is a heavy I/O user; and on RHEL7 systems, systemd is an I/O abuser. Why? What are either of these processes doing once the system has started? I checked syslog and see no indication of a process that is being respawned.

# pidstat -d -p 1
Linux 2.6.32-358.el6.x86_64 (db05-a.intra.uibk.ac.at)   01/27/2016      _x86_64_        (8 CPU)

12:50:18 PM       PID   kB_rd/s   kB_wr/s kB_ccwr/s  Command
12:50:18 PM         1     23.76     66.67      0.77  init

# pidstat -d -C systemd
Linux 3.10.0-229.1.2.el7.x86_64 (dbmon01.uibk.ac.at)    01/27/2016      _x86_64_        (4 CPU)

12:50:59 PM   UID       PID   kB_rd/s   kB_wr/s kB_ccwr/s  Command
12:50:59 PM     0         1     10.82    220.18      3.01  systemd
12:50:59 PM     0       503      0.00      0.00      0.00  systemd-journal
12:50:59 PM     0       527      0.00      0.00      0.00  systemd-udevd
12:50:59 PM     0       730      0.00      0.00      0.00  systemd-logind

As @sourcejedi and a colleague suggested: attach to the process with strace. They were just listening on a socket. systemd was doing a little more than that, but only very low levels of reading. Possibly some days before on each system, something "happened", but only these traces remain.

  • 1
    That's rather interesting but I think you need more specific data! systemd on my Fedora laptop is fine. strace -p1 -etrace=file,desc? – sourcejedi Jan 27 '16 at 14:02

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