02b568414d
We hit page allocation failures a lot at random for VM tests, in case of my own Hydra when it comes to the installer tests. The reason for this is that once the memory of the VM gets heavily fragmented the kernel is unable to allocate new pages. Setting vm.min_free_kbytes to 16MB forces the kernel to keep a minimum of 16 MB free. I've done some testing accross repeated runs of the installer tests with and without vm.min_free_kbytes set. So accross 30 test runs for each settings, all of the tests with the option being set passed while 14 tests without that sysctl option triggered page allocation failures. Sure, running 30 tests is not a guarantee that 16MB is enough, but we'll see how it turns out in the long run across all VM tests. Signed-off-by: aszlig <aszlig@redmoonstudios.org>
115 lines
3.7 KiB
Nix
115 lines
3.7 KiB
Nix
# This module allows the test driver to connect to the virtual machine
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# via a root shell attached to port 514.
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{ config, lib, pkgs, ... }:
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with lib;
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let kernel = config.boot.kernelPackages.kernel; in
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{
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config = {
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systemd.services.backdoor =
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{ wantedBy = [ "multi-user.target" ];
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requires = [ "dev-hvc0.device" "dev-ttyS0.device" ];
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after = [ "dev-hvc0.device" "dev-ttyS0.device" ];
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script =
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''
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export USER=root
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export HOME=/root
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export DISPLAY=:0.0
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source /etc/profile
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cd /tmp
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exec < /dev/hvc0 > /dev/hvc0
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while ! exec 2> /dev/ttyS0; do sleep 0.1; done
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echo "connecting to host..." >&2
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stty -F /dev/hvc0 raw -echo # prevent nl -> cr/nl conversion
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echo
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PS1= exec /bin/sh
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'';
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serviceConfig.KillSignal = "SIGHUP";
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};
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# Prevent agetty from being instantiated on ttyS0, since it
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# interferes with the backdoor (writes to ttyS0 will randomly fail
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# with EIO). Likewise for hvc0.
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systemd.services."serial-getty@ttyS0".enable = false;
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systemd.services."serial-getty@hvc0".enable = false;
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# Don't use a pager when executing backdoor actions. Because we
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# use a tty, commands like systemctl or nix-store get confused
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# into thinking they're running interactively.
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environment.variables.PAGER = "";
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boot.initrd.postDeviceCommands =
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''
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# Using acpi_pm as a clock source causes the guest clock to
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# slow down under high host load. This is usually a bad
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# thing, but for VM tests it should provide a bit more
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# determinism (e.g. if the VM runs at lower speed, then
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# timeouts in the VM should also be delayed).
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echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource
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'';
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boot.postBootCommands =
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''
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# Panic on out-of-memory conditions rather than letting the
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# OOM killer randomly get rid of processes, since this leads
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# to failures that are hard to diagnose.
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echo 2 > /proc/sys/vm/panic_on_oom
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# Coverage data is written into /tmp/coverage-data.
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mkdir -p /tmp/xchg/coverage-data
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'';
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# If the kernel has been built with coverage instrumentation, make
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# it available under /proc/gcov.
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boot.kernelModules = [ "gcov-proc" ];
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# Panic if an error occurs in stage 1 (rather than waiting for
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# user intervention).
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boot.kernelParams =
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[ "console=ttyS0" "panic=1" "boot.panic_on_fail" ];
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# `xwininfo' is used by the test driver to query open windows.
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environment.systemPackages = [ pkgs.xorg.xwininfo ];
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# Log everything to the serial console.
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services.journald.extraConfig =
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''
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ForwardToConsole=yes
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MaxLevelConsole=debug
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'';
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# Don't clobber the console with duplicate systemd messages.
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systemd.extraConfig = "ShowStatus=no";
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boot.consoleLogLevel = 7;
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# Make sure we don't hit page allocation failures if the VM's memory is
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# heavily fragmented.
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boot.kernel.sysctl."vm.min_free_kbytes" = 16384;
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# Prevent tests from accessing the Internet.
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networking.defaultGateway = mkOverride 150 "";
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networking.nameservers = mkOverride 150 [ ];
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systemd.globalEnvironment.GCOV_PREFIX = "/tmp/xchg/coverage-data";
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system.requiredKernelConfig = with config.lib.kernelConfig; [
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(isYes "SERIAL_8250_CONSOLE")
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(isYes "SERIAL_8250")
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(isEnabled "VIRTIO_CONSOLE")
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];
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networking.usePredictableInterfaceNames = false;
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# Make it easy to log in as root when running the test interactively.
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users.extraUsers.root.initialHashedPassword = mkOverride 150 "";
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};
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}
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