this renders the same in the manpage and a little more clearly in the
html manual. in the manpage there continues to be no distinction from
regular text, the html manual gets code-type markup (which was probably
the intention for most of these uses anyway).
we can't embed syntactic annotations of this kind in markdown code
blocks without yet another extension. replaceable is rare enough to make
this not much worth it, so we'll go with «thing» instead. the module
system already uses this format for its placeholder names in attrsOf
paths.
This avoids putting a large disk image in the store (and possibly
in a binary cache), while improving runtime performance.
Assuming you're running an SSD, and/or with plenty of cache (?)
it is feasible to preempt the virtualization overhead before
VM start, in single-digit seconds.
For some tests that perform many reads on the store, the improved
performance of EROFS is sufficient that not only the image creation
overhead is compensated for, but is actually faster.
Stats for nixosTests.gitlab:
Baseline without useNixStoreImage: >1000s
Baseline with useNixStoreImage without writableStore = false
ext4 image in store: 277 seconds
+ significant image build time and/or disk space
Disposable erofs image: 249 seconds _including_ image build time
Custom erofs overlay on 9p host store: 391 seconds; presumably
because the overlay still performs too many 9p accesses, or perhaps
some other overhead. This solution had no obvious performance
advantage, while requiring extra options to work, so it was
discarded.
Potential use cases for disabling `useDefaultFilesystems` include:
- Testing with uncommon filesystem layouts
- Testing scenarios where swapping occurs
- Testing with LUKS-encrypted disks
Closes#177963
While doing kernel development with the nixos testing infrastructure, it
is useful to quickly compile the kernel on the side and boot it in the testing VM.
This patch allows overriding the kernel through the environment
variable. For example, the following:
$ NIXPKGS_QEMU_KERNEL_testvm=$LINUX_SRC/arch/x86/boot/bzImage $VM/bin/nixos-test-driver
runs testvm testing VM with the fresh kernel compiled in $LINUX_SRC.
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
most modules can be evaluated for their documentation in a very
restricted environment that doesn't include all of nixpkgs. this
evaluation can then be cached and reused for subsequent builds, merging
only documentation that has changed into the cached set. since nixos
ships with a large number of modules of which only a few are used in any
given config this can save evaluation a huge percentage of nixos
options available in any given config.
in tests of this caching, despite having to copy most of nixos/, saves
about 80% of the time needed to build the system manual, or about two
second on the machine used for testing. build time for a full system
config shrank from 9.4s to 7.4s, while turning documentation off
entirely shortened the build to 7.1s.
by default a ps/2 keyboard input is used which seems to cause issues
on aarch64-linux when the machine is used high load, causing the keymap
qwertz test to always fail and azerty to sometimes fail
See https://github.com/NixOS/nixpkgs/issues/147294
the default hasn't been changed since 2009
this can improve our test performances
nixos/tests: remove explicit memorySize <1024
1024MiB is now the default
The default has been unchanged for a decade. Space is cheaper and
software catches up with that. Let's not make our testing harder
than necessary by default.
qemu_kvm is only built for one architecture, so it's smaller and takes
MUCH less time to build if it has to be built from source. And this
module doesn't support running a VM for one architecture from another
architecture, so the one architecture is all we'll need.
pathsInNixDB isn't a very accurate name when a Nix store image is
built (virtualisation.useNixStoreImage); rename it to additionalPaths,
which should be general enough to cover both cases.
Add the `useNixStoreImage` option, allowing a disk image with the
necessary contents from the Nix store to be built using
make-disk-image.nix. The image will be mounted at `/nix/store` and
acts as a drop-in replacement for the usual 9p mounting of the host's
Nix store.
This removes the performance penalty of 9p, drastically improving
execution speed of applications which do lots of reads from the Nix
store. The caveats are increased disk space usage and image build
time.
I realized quite recently that running a test VM - as documented in the
manual - like
QEMU_NET_OPTS='hostfwd=tcp::8080-:80' ./result/bin/nixos-run-vms
doesn't work anymore on `master`. After bisecting I realized that the
introduction of a forward-port option[1] is the problem since it adds a
trailing comma even if no forwarding options are specified via
`virtualisation.forwardPorts`. In that case, the networking options
would look like `-netdev user,id=user.0,,hostfwd=tcp::8080-:80' which
confused QEMU and thus the VM refused to start.
Now, the trailing comma is only added if additional port forwards are
specified declaratively.
[1] b8bfc81d5b
The current name is misleading: it doesn't contain cli arguments,
but several constants and utility functions related to qemu.
This commit also removes the use of `with import ...` for clarity.
