We have had background session class for a long time (since commit
e2acb67baa), but so far the only difference in handling of background
sessions was logging, i.e. we log some messages with LOG_DEBUG for such
sessions.
Previously there were complains [1] about excessive logging for each
time cron session is started. We used to advise user to enable lingering
for users if they want to avoid these log messages. However, on servers
with a lot of users the extra processes that result from lingering just
adds too much overhead. Hence I think that our current handling of
background sessions is not ideal and we should make better use of this
attribute.
This commit introduces a change in default behavior of logind. Logind is
now not going to start user instance of systemd when background session
is created and that should address excessive logging problem for cron
where background class is used by default. When the same user actually
logs in normally then user instance will be started as previously.
Also note that PAM_TTY variable is now always set to some value for PAM
sessions started via PAMName= option. Otherwise we would categorize such
sessions as "background" and user manager won't be started.
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1825942
Fixes#21764.
I think is very simple, but flexible. The date may be set early, for distros
that have a fixed schedule, but it doesn't have to. So for example Debian could
push out an update that sets a few months before the release goes EOL. And
various tools, in particular graphical desktops, can start nagging people to
upgrade a few weeks before the date.
As discussed in the bug, we don't need granularity higher than a day. And this
means that we can use a simple human- and machine-readable format.
I was considering other names, e.g. something with "EOL", but I think that
"SUPPORT_END" is better because it doesn't imply that the machine will somehow
stop working. This is supposed to be an advisory, nothing more.
NetworkManager takes systemd sources. It gets compiler warnings
related to _fallthrough_. They probably can also affect systemd
itself.
A) on RHEL-7, gcc 4.8.5-44.el7 we get:
../src/libnm-systemd-shared/src/fundamental/macro-fundamental.h:45:22: error: "__clang__" is not defined [-Werror=undef]
#if __GNUC__ >= 7 || __clang__
^
Presumably gcc older than 7 is supported, so fix this.
B) on Ubuntu 18.04, clang 1:6.0-41~exp5~ubuntu1 we get:
../src/libnm-systemd-core/src/libsystemd-network/sd-dhcp6-client.c:746:17: error: declaration does not declare anything [-Werror,-Wmissing-declarations]
_fallthrough_;
^
../src/libnm-systemd-shared/src/fundamental/macro-fundamental.h:46:25: note: expanded from macro '_fallthrough_'
# define _fallthrough_ __attribute__((__fallthrough__))
^
Granted, README comments that clang >= 10 is required. However,
parts of systemd build just fine with older clang. It seems unnecessary
to break this and the fix helps NetworkManager.
Fixes: c0f5d58c9a ('meson: Document why -Wimplicit-fallthrough is not used with clang')
This fixes formatting of JSON real values, and uses C locale for them.
It's kinda interesting that this wasn't noticed before: the C locale
object we allocated was not used, hence doing the dance had zero effect.
This makes "test-varlink" pass again on systems with non-C locale.
(My guess: noone noticed this because "long double" was used before by
the JSON code and that had no locale supporting printer or so?)
So far we didn't enable the cpu controller because of overhead of the
accounting. If I'm reading things correctly, delegation was enabled for a while
for the units with user and pam context set, i.e. for user@.service too.
a931ad47a8 added the explicit Delegate=yes|no
switch, but it was initially set to 'yes'.
acc8059129 disabled delegation for user@.service
with the justication that CPU accounting is expensive, but half a year later
a88c5b8ac4 changed DefaultCPUAccounting=yes for
kernels >=4.15 with the justification that CPU accounting is inexpensive there.
In my (very noncomprehensive) testing, I don't see a measurable overhead if the
cpu controller is enabled for user slices. I tried some repeated compilations,
and there is was no statistical difference, but the noise level was fairly
high. Maybe better benchmarking would reveal a difference.
The goal of this change is very simple: currently all of the user session,
including services like the display server and pipewire are under user@.service.
This means that when e.g. a compilation job is started in the session's
app.slice, the processes in session.slice compete for CPU and can be starved.
In particular, audio starts to stutter, etc. With CPU controller enabled,
I can start start 'ninja -C build -j40' in a tab and this doesn't have any
noticable effect on audio.
I don't think the particular values matter too much: the CPU controller is
work-convserving, and presumably the session slice would never need more than
e.g. one 1 full CPU, i.e. half or a quarter of available CPU resources on even
the smallest of today's machines. app.slice and session.slice are assigned
equal weights, background.slice is assigned a smaller fraction. CPUWeight=100
is the default, but I wrote it explicitly to make it easier for users to see
how the split is done. So effectively this should result in session.slice
getting as much power as it needs.
If if turns out that this does have a noticable overhead, we could make it
opt-in. But I think that the benefit to usability is important enough to enable
it by default. W/o something like this the session is not really usable with
background tasks.
We now have a local implementation in string-util-fundamental.c, but
it's useful at a lot of other places, hence let's give it a more
expressive name and share it across the tree.
Follow-up for: 8d9156660d
The "Networking" section has a lonely single document listed right now,
even though the "Concepts" section has two more network related docs.
Move them over, let's end this loneliness.
On Ubuntu, cryptsetup does not link against libgcc_s.so.1 which leads to
the following test failure in TEST-70-TPM2:
systemd[1]: Starting testsuite-70.service...
systemd[329]: testsuite-70.service: Executing: /usr/lib/systemd/tests/testdata/units/testsuite-70.sh
testsuite-70.sh[329]: + export SYSTEMD_LOG_LEVEL=debug
testsuite-70.sh[329]: + SYSTEMD_LOG_LEVEL=debug
testsuite-70.sh[329]: + img=/var/tmp/test.img
testsuite-70.sh[329]: + dd if=/dev/zero of=/var/tmp/test.img bs=1024k count=20 status=none
testsuite-70.sh[329]: + echo -n passphrase
testsuite-70.sh[329]: + cryptsetup luksFormat -q --use-urandom /var/tmp/test.img /tmp/passphrase
testsuite-70.sh[333]: libgcc_s.so.1 must be installed for pthread_exit to work
testsuite-70.sh[329]: /usr/lib/systemd/tests/testdata/units/testsuite-70.sh:
line 12: 333 Aborted (core dumped) cryptsetup luksFormat -q --use-urandom $img /tmp/passphrase
To fix this, manually install libgcc_s.so.1 to the test image if running
on Debian-like systems.
When we start, the contents of the variable match the name. But then
in the loop, the variable doesn't point at the old head any more. So let's
rename it to something with a plural.
