Linux 6.18 Will Fix Lockups When Systemd Units Read Lots of Files

  MOUNT(8)       
       relatime
           Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than or equal to the current
           modify or change time. (Similar to noatime, but it doesn’t break mutt(1) or other applications that need to know if a file has been read since the last time it
           was modified.)

           Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless noatime was specified), and the strictatime option is required to
           obtain traditional semantics. In addition, since Linux 2.6.30, the file’s last access time is always updated if it is more than 1 day old.

Maybe if you could taint a process (or perhaps the inode and/or path instead) so that its and its children's opens get the new o_atime flag by default, so that systemd or whatever could set it for legacy processes (or files/paths) that need it.

Then distros or SRE's could put up with it without nagging all the SWEs about linuxisms. Some of whom may not know or care their code runs on linux.

You can do that with bpf tooling now, for example the `opensnoop` BCC program can capture all file opens on demand. You can also write tools which capture all POSIX IOs to specific files/directories. I can see atime sometimes being useful in some super niche use cases such as hisenbugs you cannot reproduce reliably, but I would be reaching for BPF tools first.

I’d say it’s both a systemd issue and a kernel issue. The fact that systemd motivates kernel fixes does point to systemd being maybe just a bit overengineered