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In cgroup v2 we have protection tunables -- currently MemoryLow and
MemoryMin (there will be more in future for other resources, too). The
design of these protection tunables requires not only intermediate
cgroups to propagate protections, but also the units at the leaf of that
resource's operation to accept it (by setting MemoryLow or MemoryMin).
This makes sense from an low-level API design perspective, but it's a
good idea to also have a higher-level abstraction that can, by default,
propagate these resources to children recursively. In this patch, this
happens by having descendants set memory.low to N if their ancestor has
DefaultMemoryLow=N -- assuming they don't set a separate MemoryLow
value.
Any affected unit can opt out of this propagation by manually setting
`MemoryLow` to some value in its unit configuration. A unit can also
stop further propagation by setting `DefaultMemoryLow=` with no
argument. This removes further propagation in the subtree, but has no
effect on the unit itself (for that, use `MemoryLow=0`).
Our use case in production is simplifying the configuration of machines
which heavily rely on memory protection tunables, but currently require
tweaking a huge number of unit files to make that a reality. This
directive makes that significantly less fragile, and decreases the risk
of misconfiguration.
After this patch is merged, I will implement DefaultMemoryMin= using the
same principles.
Some controllers (like the CPU controller) have a performance cost that
is non-trivial on certain workloads. While this can be mitigated and
improved to an extent, there will for some controllers always be some
overheads associated with the benefits gained from the controller.
Inside Facebook, the fix applied has been to disable the CPU controller
forcibly with `cgroup_disable=cpu` on the kernel command line.
This presents a problem: to disable or reenable the controller, a reboot
is required, but this is quite cumbersome and slow to do for many
thousands of machines, especially machines where disabling/enabling a
stateful service on a machine is a matter of several minutes.
Currently systemd provides some configuration knobs for these in the
form of `[Default]CPUAccounting`, `[Default]MemoryAccounting`, and the
like. The limitation of these is that Default*Accounting is overrideable
by individual services, of which any one could decide to reenable a
controller within the hierarchy at any point just by using a controller
feature implicitly (eg. `CPUWeight`), even if the use of that CPU
feature could just be opportunistic. Since many services are provided by
the distribution, or by upstream teams at a particular organisation,
it's not a sustainable solution to simply try to find and remove
offending directives from these units.
This commit presents a more direct solution -- a DisableControllers=
directive that forcibly disallows a controller from being enabled within
a subtree.
There isn't really much need to keep them separate. Anything which is a good
corpus entry can be used as a smoke test, and anything which which is a
regression test can just as well be inserted into the corpus.
The only functional difference from this patch (apart from different paths in
output) is that the regression tests are now zipped together with the rest of
the corpus.
$ meson configure build -Dslow-tests=true && ninja -C build test
...
307/325 fuzz-dns-packet:issue-7888:address OK 0.06 s
308/325 fuzz-dns-packet:oss-fuzz-5465:address OK 0.04 s
309/325 fuzz-journal-remote:crash-5a8f03d4c3a46fcded39527084f437e8e4b54b76:address OK 0.07 s
310/325 fuzz-journal-remote:crash-96dee870ea66d03e89ac321eee28ea63a9b9aa45:address OK 0.05 s
311/325 fuzz-journal-remote:oss-fuzz-8659:address OK 0.05 s
312/325 fuzz-journal-remote:oss-fuzz-8686:address OK 0.07 s
313/325 fuzz-unit-file:oss-fuzz-6884:address OK 0.06 s
314/325 fuzz-unit-file:oss-fuzz-6885:address OK 0.05 s
315/325 fuzz-unit-file:oss-fuzz-6886:address OK 0.05 s
316/325 fuzz-unit-file:oss-fuzz-6892:address OK 0.05 s
317/325 fuzz-unit-file:oss-fuzz-6897:address OK 0.05 s
318/325 fuzz-unit-file:oss-fuzz-6897-evverx:address OK 0.06 s
319/325 fuzz-unit-file:oss-fuzz-6908:address OK 0.07 s
320/325 fuzz-unit-file:oss-fuzz-6917:address OK 0.07 s
321/325 fuzz-unit-file:oss-fuzz-6977:address OK 0.13 s
322/325 fuzz-unit-file:oss-fuzz-6977-unminimized:address OK 0.12 s
323/325 fuzz-unit-file:oss-fuzz-7004:address OK 0.05 s
324/325 fuzz-unit-file:oss-fuzz-8064:address OK 0.05 s
325/325 fuzz-unit-file:oss-fuzz-8827:address OK 0.52 s
We have "installed tests", but don't provide an easy way to run them.
The protocol is very simple: each test must return 0 for success, 77 means
"skipped", anything else is an error. In addition, we want to print test
output only if the test failed.
I wrote this simple script. It is pretty basic, but implements the functions
listed above. Since it is written in python it should be easy to add option
parsing (like running only specific tests, or running unsafe tests, etc.)
I looked at the following alternatives:
- Ubuntu root-unittests: this works, but just dumps all output to the terminal,
has no coloring.
- @ssahani's test runner [2]
It uses the unittest library and the test suite was implented as a class, and
doesn't implement any of the functions listed above.
- cram [3,4]
cram runs our tests, but does not understand the "ignore the output" part,
has not support for our magic skip code (it uses hardcoded 80 instead),
and seems dead upstream.
- meson test
Here the idea would be to provide an almost-empty meson.build file under
/usr/lib/systemd/tests/ that would just define all the tests. This would
allow us to reuse the test runner we use normally. Unfortunately meson requires
a build directory and configuration to be done before running tests. This
would be possible, but seems a lot of effort to just run a few binaries.
[1] 242c96addb/debian/tests/root-unittests
[2] https://github.com/systemd/systemd-fedora-ci/blob/master/upstream/systemd-upstream-tests.py
[3] https://bitheap.org/cram/
[4] https://pypi.org/project/pytest-cram/Fixes#10069.
Back in 08318a2c5a, value "false" was enabled for
'-Dtests=', but various tests were not conditionalized properly. So even with
-Dtests=false -Dslow-tests=false we'd run 120 tests. Let's make this consistent.
Absolute paths make everything simple and quick, but sometimes this requirement
can be annoying. A good example is calling 'test', which will be located in
/usr/bin/ or /bin depending on the distro. The need the provide the full path
makes it harder a portable unit file in such cases.
This patch uses a fixed search path (DEFAULT_PATH which was already used as the
default value of $PATH), and if a non-absolute file name is found, it is
immediately resolved to a full path using this search path when the unit is
loaded. After that, everything behaves as if an absolute path was specified. In
particular, the executable must exist when the unit is loaded.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
The unit files for test-execute are named like
`exec-(setting-name-in-lower-character)-(optional-text).service`.
However, test units for AmbientCapabilities= are not following this.
So, let's rename them for the consistency.
This does not change anything in the functionality of the test.
The nobody user/group may not synthesized by systemd.
To run tests the functionalities in such situation, this adds tests
by user/group by daemon, as it is expected to exists all environments.
This is a bit painful because a separate build of systemd is necessary. The
tests are guarded by tests!=false and slow-tests==true. Running them is not
slow, but compilation certainly is. If this proves unwieldy, we can add a
separate option controlling those builds later.
The build for each sanitizer has its own directory, and we build all fuzzer
tests there, and then pull them out one-by-one by linking into the target
position as necessary. It would be nicer to just build the desired fuzzer, but
we need to build the whole nested build as one unit.
[I also tried making systemd and nested meson subproject. This would work
nicely, but meson does not allow that because the nested target names are the
same as the outer project names. If that is ever fixed, that would be the way
to go.]
v2:
- make sure things still work if memory sanitizer is not available
v3:
- switch to syntax which works with meson 0.42.1 found in Ubuntu
We currently look for "nobody" and "nfsnobody" when testing groups, both
of which do not exist on Ubuntu, our main testing environment. Let's
extend the tests slightly to also use "nogroup" if it exists.
So far I avoided adding license headers to meson files, but they are pretty
big and important and should carry license headers like everything else.
I added my own copyright, even though other people modified those files too.
But this is mostly symbolic, so I hope that's OK.
The configuration option was called -Dresolve, but the internal define
was …RESOLVED. This options governs more than just resolved itself, so
let's settle on the version without "d".
The advantage is that is the name is mispellt, cpp will warn us.
$ git grep -Ee "conf.set\('(HAVE|ENABLE)_" -l|xargs sed -r -i "s/conf.set\('(HAVE|ENABLE)_/conf.set10('\1_/"
$ git grep -Ee '#ifn?def (HAVE|ENABLE)' -l|xargs sed -r -i 's/#ifdef (HAVE|ENABLE)/#if \1/; s/#ifndef (HAVE|ENABLE)/#if ! \1/;'
$ git grep -Ee 'if.*defined\(HAVE' -l|xargs sed -i -r 's/defined\((HAVE_[A-Z0-9_]*)\)/\1/g'
$ git grep -Ee 'if.*defined\(ENABLE' -l|xargs sed -i -r 's/defined\((ENABLE_[A-Z0-9_]*)\)/\1/g'
+ manual changes to meson.build
squash! build-sys: use #if Y instead of #ifdef Y everywhere
v2:
- fix incorrect setting of HAVE_LIBIDN2
