They are somewhat similar, but not easy to discover, esp. considering that
they are described in different pages.
For PrivateDevices=, split out the first paragraph that gives the high-level
overview. (The giant second paragraph could also use some heavy editing to break
it up into more digestible chunks, alas.)
In most of our codebase when we referenced "ipv4" and "ipv6" on the
right-hand-side of an assignment, we lowercases it (on the
left-hand-side we used CamelCase, and thus "IPv4" and "IPv6"). In
particular all across the networkd codebase the various "per-protocol
booleans" use the lower-case spelling. Hence, let's use lower-case for
SocketBindAllow=/SocketBindDeny= too, just make sure things feel like
they belong together better.
(This work is not included in any released version, hence let's fix this
now, before any fixes in this area would be API breakage)
Follow-up for #17655
systemd.unit(5) is a wall of text. And this particular feature can be very useful
in the context of resource control. Let's avertise this cool feature a bit more.
Fixes#17900.
The description didn't really explain how the distribution mechanism
works exactly and the relationship of leaf and slice units.
Update the documentation and also explicitly explain the expected
behaviour as it is created by the memory_recursiveprot cgroup2 mount
option.
https://tools.ietf.org/html/draft-knodel-terminology-02https://lwn.net/Articles/823224/
This gets rid of most but not occasions of these loaded terms:
1. scsi_id and friends are something that is supposed to be removed from
our tree (see #7594)
2. The test suite defines an API used by the ubuntu CI. We can remove
this too later, but this needs to be done in sync with the ubuntu CI.
3. In some cases the terms are part of APIs we call or where we expose
concepts the kernel names the way it names them. (In particular all
remaining uses of the word "slave" in our codebase are like this,
it's used by the POSIX PTY layer, by the network subsystem, the mount
API and the block device subsystem). Getting rid of the term in these
contexts would mean doing some major fixes of the kernel ABI first.
Regarding the replacements: when whitelist/blacklist is used as noun we
replace with with allow list/deny list, and when used as verb with
allow-list/deny-list.
The document is rather huge, and a specific link is easier to consume. The form
is a bit strange because troff puts the symlink at the bottom, keyed by title,
so we need to use the same link target in all places.
When wrong element types are used, directives are sometimes placed in the wrong
section. Also, strip part of text starting with "'", which is used in a few
places and which is displayed improperly in the index.
Introduce support for configuring cpus and mems for processes using
cgroup v2 CPUSET controller. This allows users to limit which cpus
and memory NUMA nodes can be used by processes to better utilize
system resources.
The cgroup v2 interfaces to control it are cpuset.cpus and cpuset.mems
where the requested configuration is written. However, it doesn't mean
that the requested configuration will be actually used as parent cgroup
may limit the cpus or mems as well. In order to reflect the real
configuration cgroup v2 provides read-only files cpuset.cpus.effective
and cpuset.mems.effective which are exported to users as well.
Don't claim we'd use cgroup.deny much. It's just a way to remove stuff
from device lists, which is nothing we allow users to explicitly
configure.
Also, extend documentation when wildcards may be used, and when not.
Takes a single /sys/fs/bpf/pinned_prog string as argument, but may be
specified multiple times. An empty assignment resets all previous filters.
Closes https://github.com/systemd/systemd/issues/10227
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.
The "include" files had type "book" for some raeason. I don't think this
is meaningful. Let's just use the same everywhere.
$ perl -i -0pe 's^..DOCTYPE (book|refentry) PUBLIC "-//OASIS//DTD DocBook XML V4.[25]//EN"\s+"http^<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"\n "http^gms' man/*.xml
No need to waste space, and uniformity is good.
$ perl -i -0pe 's|\n+<!--\s*SPDX-License-Identifier: LGPL-2.1..\s*-->|\n<!-- SPDX-License-Identifier: LGPL-2.1+ -->|gms' man/*.xml
This new setting allows configuration of CFS period on the CPU cgroup, instead
of using a hardcoded default of 100ms.
Tested:
- Legacy cgroup + Unified cgroup
- systemctl set-property
- systemctl show
- Confirmed that the cgroup settings (such as cpu.cfs_period_ns) were set
appropriately, including updating the CPU quota (cpu.cfs_quota_ns) when
CPUQuotaPeriodSec= is updated.
- Checked that clamping works properly when either period or (quota * period)
are below the resolution of 1ms, or if period is above the max of 1s.
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.
The original manpage says "Implies BBBAccounting" many times but actually that accounting is not implied by the respective resource control in v239 with the unified cgroup hierarchy. This commit removes those false explanations.
