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I have an XPS 13 Developer Edition Dell Laptop running Debian GNU/Linux Jessie (testing).

When the laptop starts up on battery power, the keyboard is so unresponsive that it is a real struggle to type in my password (key presses are delayed, ignored or stick and repeat many times).

It's OK if it's running off the mains, even if I boot with the battery and then plug it in.

I've not customised the default service configs (except trivial changes unrelated to this) and I keep my full list of debfoster keepers on github if you'd like to see the services I have running.

How can I set the default laptop battery mode to be something usable?

As requested, systemd-analyze blame shows

       1.084s kbd.service
       394ms exim4.service
       303ms NetworkManager.service
       190ms ModemManager.service
       179ms loadcpufreq.service
       163ms laptop-mode.service
       147ms accounts-daemon.service
       129ms console-setup.service
       117ms networking.service
       100ms lightdm.service
        98ms bluetooth.service
        97ms systemd-logind.service
        93ms keyboard-setup.service
        89ms avahi-daemon.service
        85ms systemd-fsck-root.service
        73ms gpm.service

and 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 @2.434s
??multi-user.target @2.434s
  ??exim4.service @2.074s +358ms
    ??basic.target @2.070s
      ??timers.target @2.069s
        ??systemd-tmpfiles-clean.timer @2.069s
          ??sysinit.target @2.069s
            ??console-setup.service @1.936s +132ms
              ??kbd.service @531ms +1.403s
                ??remote-fs.target @531ms
                  ??local-fs.target @530ms
                    ??tmp.mount @524ms +5ms
                      ??systemd-fsck@dev-disk-by\x2duuid-a2cf7f78\x2d691b\x2d4c01\x2da80c\x2d1bc6228230a5.service @466ms +57ms
                        ??dev-disk-by\x2duuid-a2cf7f78\x2d691b\x2d4c01\x2da80c\x2d1bc6228230a5.device @465ms

but this seems consistent with and without the mains power supply.

Some more info:

  • I don't experience the keyboard lag if I drop to a TTY.
  • I have performed a cpufreg-aperf both with and without mains and the results are similar when the machine is idle or I'm just typing in the terminal.
  • some people have claimed that disabling USB autosuspend helps, but I have the same problem even after disabling it entirely and rebooting.
  • once I plug in the mains and then unplug it, the problem goes away.
  • forcing the performance cpu scaler (even on battery) doesn't help
  • external USB keyboards are unaffected

Some hardware info:

lsusb
Bus 001 Device 002: ID 8087:8000 Intel Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 004: ID 8087:07dc Intel Corp. 
Bus 002 Device 003: ID 0bda:5604 Realtek Semiconductor Corp. 
Bus 002 Device 002: ID 06cb:0af8 Synaptics, Inc. 
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

 xinput
? Virtual core pointer                      id=2    [master pointer  (3)]
?   ? Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
?   ? SYNAPTICS Synaptics Large Touch Screen    id=9    [slave  pointer  (2)]
?   ? SynPS/2 Synaptics TouchPad                id=12   [slave  pointer  (2)]
? Virtual core keyboard                     id=3    [master keyboard (2)]
    ? Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
    ? Power Button                              id=6    [slave  keyboard (3)]
    ? Video Bus                                 id=7    [slave  keyboard (3)]
    ? Power Button                              id=8    [slave  keyboard (3)]
    ? Integrated Webcam                         id=10   [slave  keyboard (3)]
    ? AT Translated Set 2 keyboard              id=11   [slave  keyboard (3)]
    ? Dell WMI hotkeys                          id=13   [slave  keyboard (3)]
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    You first have to diagnose the cause of the lag; what does systemd-analyze {blame,critical-chain} show? – jasonwryan Sep 12 '14 at 21:53
  • I've updated as requested, but I'm not sure how this can help. The startup time itself is not the problem, it's that the response of a key press to the key being interpreted is so slow that the keys overlap and typing anything coherent is very difficult. – fommil Sep 12 '14 at 22:35
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    They are two separate commands... In any event, does your issue exist only in X, or in the TTY as well? – jasonwryan Sep 12 '14 at 22:48
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    @fommil - Jason wrote the commands in a compact form (I believe). It's actually 2 commands: systemd-analyze blame and systemd-analyze critical-chain. The notation {blame,critical-chain} is meant to denote that you'd provide arg1 to the command and arg2 to the command. – slm Sep 13 '14 at 1:34
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    What happens if you use an external keyboard, e.g. usb and try logging in with that. This is for diagnosis not an answer. – Michael Durrant Sep 13 '14 at 16:14
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UPDATE the below didn't make the problem go away, but upgrading to linux kernel 3.16 has had a dramatic improvement!

I solved this while figuring out a related problem! why is my laptop-mode configuration being ignored?

It turns out that the default "min CPU freq" is set to 0% for Intel pstate devices. I bumped it to 5% and the key lag went away.

Thanks all for your helpful suggestions! This has actually been bugging me ever since I got the laptop nearly 6 months ago.

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