The way the various properties[] arrays are initialized is inefficient:
- only the .data members change at runtime, yet the whole arrays of
properties with all the fields are constructed on the stack one by
one by the code.
- there's duplication, eg. the properties of "org.freedesktop.systemd1.Unit"
are repeated in several unit types.
Fix it by moving the information about properties into static const
sections. Instead of storing the .data directly in the property, store
a constant offset from a run-time base.
The small arrays of struct BusBoundProperties bind together the constant
information with the right runtime information (the base pointer).
On my system the code shrinks by 60 KB, data increases by 10 KB.
Now that objects of all unit types are allocated the exact amount of
memory they need, the Unit union has lost its purpose. Remove it.
"Unit" is a more natural name for the base unit class than "Meta", so
rename Meta to Unit.
Access to members of the base class gets simplified.
The storage of the unit objects on the heap is currently not very
efficient. For every unit object we allocate a chunk of memory as large
as the biggest unit type, although there are significant differences in
the units' real requirements.
pahole shows the following sizes of structs:
488 Target
496 Snapshot
512 Device
528 Path
560 Timer
576 Automount
1080 Socket
1160 Swap
1168 Service
1280 Mount
Usually there aren't many targets or snapshots in the system, but Device
is one of the most common unit types and for every one we waste
1280 - 512 = 768 bytes.
Fix it by allocating only the right amount for the given unit type.
On my machine (x86_64, with 39 LVM volumes) this decreases systemd's
USS (unique set size) by more than 300 KB.
quotacheck.service and quotaon.service were not pulled in for fstab mounts.
Fix it by not clearing the default_dependencies flag.
The root filesystem may have quotas too, so don't check for "/" there.
No need to have duplicate code for adding dependencies on umount.target.
https://bugzilla.redhat.com/show_bug.cgi?id=773431
