TasksMax can't be set more than 16384 for a nspawn machine

[level-a]

systemd version the issue has been seen with

252

Used distribution

Debian Bookworm

Linux kernel version used

6.5.0-0.deb12.4-amd64

CPU architectures issue was seen on

None

Component

machinectl

Expected behaviour you didn't see

override default TasksMax=16384 set in /lib/systemd/system/systemd-nspawn@.service has no effect

Unexpected behaviour you saw

No response

Steps to reproduce the problem

set higher TasksMax limit and try to fork more than 16384 processes in nspawn
looks like this limit hit

systemd/src/machine/machine.c

Line 420 in 2b21482

"TasksMax", "t", UINT64_C(16384));

Additional program output to the terminal or log subsystem illustrating the issue

cat /sys/fs/cgroup/machine.slice/pids.peak 
16385

[Sat May 13 19:43:51 2024] cgroup: fork rejected by pids controller in /machine.slice/machine-puppet001.scope/payload/system.slice/system-puppetserver.slice/puppetserver@003.service



systemctl show systemd-nspawn@puppet001 | rg TasksMax
TasksMax=262144

sudo dmesg | grep pid_max
[    0.225209] pid_max: default: 262144 minimum: 2048

cat /sys/fs/cgroup/machine.slice/pids.max
262144

cat /sys/fs/cgroup/system.slice/pids.max
262144