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.
systemd only uses functions that are as of Linux 4.15+ provided
externally to the CPU controller (currently usage_usec), so if we have a
new enough kernel, we don't need to set CGROUP_MASK_CPU for
CPUAccounting=true as the CPU controller does not need to necessarily be
enabled in this case.
Part of this patch is modelled on an earlier patch by Ryutaroh Matsumoto
(see PR #9665).
The kernel added support for a new cgroup memory controller knob memory.min in
bf8d5d52ffe8 ("memcg: introduce memory.min") which was merged during v4.18
merge window.
Add MemoryMin to support memory.min.
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
This drops needless safety checks that ensure we only reference block
devices for blockio/io settings. The backing code was already able to
accept regular file system paths too, in which case the backing device
node of that file system would be used. Hence, let's drop the artificial
restrictions and open up this underlying functionality.
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.
This improves the BPF/cgroup detection logic, and looks whether
BPF_ALLOW_MULTI is supported. This flag allows execution of multiple
BPF filters in a recursive fashion for a whole cgroup tree. It enables
us to properly report IP accounting for slice units, as well as
delegation of BPF support to units without breaking our own IP
accounting.
Currently we allowed delegation for alluntis with cgroup backing
except for slices. Let's make this a bit more strict for now, and only
allow this in service and scope units.
Let's also add a generic accessor unit_cgroup_delegate() for checking
whether a unit has delegation turned on that checks the new bool first.
Also, when doing transient units, let's explcitly refuse turning on
delegation for unit types that don#t support it. This is mostly
cosmetical as we wouldn't act on the delegation request anyway, but
certainly helpful for debugging.
systemd creates several device nodes in /run/systemd/inaccessible/.
This makes CGroup's settings related to IO can take device node
files in the directory.
Let's replace usage of fputc_unlocked() and friends by __fsetlocking(f,
FSETLOCKING_BYCALLER). This turns off locking for the entire FILE*,
instead of doing individual per-call decision whether to use normal
calls or _unlocked() calls.
This has various benefits:
1. It's easier to read and easier not to forget
2. It's more comprehensive, as fprintf() and friends are covered too
(as these functions have no _unlocked() counterpart)
3. Philosophically, it's a bit more correct, because it's more a
property of the file handle really whether we ever pass it on to another
thread, not of the operations we then apply to it.
This patch reworks all pieces of codes that so far used fxyz_unlocked()
calls to use __fsetlocking() instead. It also reworks all places that
use open_memstream(), i.e. use stdio FILE* for string manipulations.
Note that this in some way a revert of 4b61c87511.
Let's make sure that when we return a D-Bus error, we return a native
one, if we generate it ourselves, and use errno-based error
synthetization only if we received an errno ourselves. Yes, this makes
things slightly longer, but is highly misleading as we propagate D-Bus
errors, and not errnos to the client.
This majorly refactors the transient unit file and drop-in writing
logic, so that we properly C-escape and specifier-escape (% → %%)
everything we write out, so that when we read it back again, specifiers
are parsed that aren't supposed to be parsed.
This renames unit_write_drop_in() and friends by unit_write_setting().
The name change is supposed to clarify that the functions are not only
used to write drop-in files, but also transient unit files.
The previous "mode" parameter to this function is replaced by a more
generic "flags", which knows additional flags for implicit C-style and
specifier escaping before writing things out. This can cover most
properties where either form of escaping is defined. For the cases where
this isn't sufficient, we add helpers unit_escape_setting() and
unit_concat_strv() for escaping individual strings or strvs properly.
While we are at it, we also prettify generation of transient unit files:
we try to reduce the number of section headers written out: previously
we'd write the right section header our for each setting. With this
change we do so only if the setting lives in a different section than
the one before.
(This should also be considered preparation for when we add proper APIs
to systemd to write normal, persistant unit files through the bus API)
Before this, assigning empty string to Delegate= makes no change to the
controller list. This is inconsistent to the other options that take list
of strings. After this, when empty string is assigned to Delegate=, the
list of controllers is reset. Such behavior is consistent to other options
and useful for drop-in configs.
Closes#7334.
Let's reduce the amount of noise a bit, there's little point in
complaining loudly about every single unit like this, let's complain
only about the first one, and then downgrade the log level to LOG_DEBUG
for the other cases.
Fixes: #7188
Previously it was not possible to select which controllers to enable for
a unit where Delegate=yes was set, as all controllers were enabled. With
this change, this is made configurable, and thus delegation units can
pick specifically what they want to manage themselves, and what they
don't care about.
As a follow-up for db3f45e2d2 let's do the
same for all other cases where we create a FILE* with local scope and
know that no other threads hence can have access to it.
For most cases this shouldn't change much really, but this should speed
dbus introspection and calender time formatting up a bit.
We would write
[Slice]
CPUQuota=1844674407370955%
which is (numerically) correct, but it seems better to just write
[Slice]
CPUQuota=
which is interpreted as USEC_INFINITY by the parser in config_parse_cpu_quota().
Fixes#5965.
Unfortunately, due to the disagreements in the kernel development community,
CPU controller cgroup v2 support has not been merged and enabling it requires
applying two small out-of-tree kernel patches. The situation is explained in
the following documentation.
https://git.kernel.org/cgit/linux/kernel/git/tj/cgroup.git/tree/Documentation/cgroup-v2-cpu.txt?h=cgroup-v2-cpu
While it isn't clear what will happen with CPU controller cgroup v2 support,
there are critical features which are possible only on cgroup v2 such as
buffered write control making cgroup v2 essential for a lot of workloads. This
commit implements systemd CPU controller support on the unified hierarchy so
that users who choose to deploy CPU controller cgroup v2 support can easily
take advantage of it.
On the unified hierarchy, "cpu.weight" knob replaces "cpu.shares" and "cpu.max"
replaces "cpu.cfs_period_us" and "cpu.cfs_quota_us". [Startup]CPUWeight config
options are added with the usual compat translation. CPU quota settings remain
unchanged and apply to both legacy and unified hierarchies.
v2: - Error in man page corrected.
- CPU config application in cgroup_context_apply() refactored.
- CPU accounting now works on unified hierarchy.
That way, we can neatly keep this in line with the new TasksMaxScale= option.
Note that we didn't release a version with MemoryLimitByPhysicalMemory= yet,
hence this change should be unproblematic without breaking API.
This adds support for a TasksMax=40% syntax for specifying values relative to
the system's configured maximum number of processes. This is useful in order to
neatly subdivide the available room for tasks within containers.
https://github.com/systemd/systemd/pull/3685 introduced
/run/systemd/inaccessible/{chr,blk} to map inacessible devices,
this patch allows systemd running inside a nspawn container to create
/run/systemd/inaccessible/{chr,blk}.
The unit files already accept relative, percent-based memory limit
specification, let's make sure "systemctl set-property" support this too.
Since we want the physical memory size of the destination machine to apply we
pass the percentage in a new set of properties that only exist for this
purpose, and can only be set.
On the unified hierarchy, memory controller implements three control knobs -
low, high and max which enables more useable and versatile control over memory
usage. This patch implements support for the three control knobs.
* MemoryLow, MemoryHigh and MemoryMax are added for memory.low, memory.high and
memory.max, respectively.
* As all absolute limits on the unified hierarchy use "max" for no limit, make
memory limit parse functions accept "max" in addition to "infinity" and
document "max" for the new knobs.
* Implement compatibility translation between MemoryMax and MemoryLimit.
v2:
- Fixed missing else's in config_parse_memory_limit().
- Fixed missing newline when writing out drop-ins.
- Coding style updates to use "val > 0" instead of "val".
- Minor updates to documentation.
Except for per-device BlockIO, IO and DeviceAllow/Deny settings, all were
missing newline causing the next drop-in to be concatenated at the end of the
line. Fix it.
Zbigniew Jędrzejewski-Szmek