In some cases (e.g. trimmed-down chroot or containers), libudev is the
only thing needed, with udevd and assorted programs totally useless
(e.g. because /dev is bind-mounted from the real one and managed
out-side the chroot/container).
Add an option to ./configure to enable/disable building the programs;
this option defaults to "enable", so that it is backward compatible with
existing build procedure, and because it by default makes sense to have
udevd et al.
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
mallinfo is not specified by POSIX or the C standards, therefore
it's not available for all libc libraries (musl).
Add the ability to disable mallinfo statistics.
Fixes:
selinux-util.c: In function ‘mac_selinux_init’:
selinux-util.c:70:25: error: storage size of ‘before_mallinfo’ isn’t known
struct mallinfo before_mallinfo, after_mallinfo;
Signed-off-by: Romain Naour <romain.naour@openwide.fr>
* configure.ac: use LT_LIBM to check for the maths library
* src/accelerometer/Makefile.am: use $(LIBM) instead of -lm in the link
flags
This causes all executables (except accelerometer) and libraries to be
linked without libm, which they do not need.
We reintroduce hashmap.{h,c}, list.h and set.h verbatim from upstream,
before we punt dead code. The following is the upstream message:
This is a rewrite of the hashmap implementation. Its advantage is lower
memory usage.
It uses open addressing (entries are stored in an array, as opposed to
linked lists). Hash collisions are resolved with linear probing and
Robin Hood displacement policy. See the references in hashmap.c.
Some fun empirical findings about hashmap usage in systemd on my laptop:
- 98 % of allocated hashmaps are Sets.
- Sets contain 78 % of all entries, plain Hashmaps 17 %, and
OrderedHashmaps 5 %.
- 60 % of allocated hashmaps contain only 1 entry.
- 90 % of allocated hashmaps contain 5 or fewer entries.
- 75 % of all entries are in hashmaps that use trivial_hash_ops.
Clearly it makes sense to:
- store entries in distinct entry types. Especially for Sets - their
entries are the most numerous and they require the least information
to store an entry.
- have a way to store small numbers of entries directly in the hashmap
structs, and only allocate the usual entry arrays when the direct
storage is full.
The implementation has an optional debugging feature (enabled by
defining the ENABLE_HASHMAP_DEBUG macro), where it:
- tracks all allocated hashmaps in a linked list so that one can
easily find them in gdb,
- tracks which function/line allocated a given hashmap, and
- checks for invalid mixing of hashmap iteration and modification.
Since entries are not allocated one-by-one anymore, mempools are not
used for entries. Originally I meant to drop mempools entirely, but it's
still worth it to use them for the hashmap structs. My testing indicates
that it makes loading of units about 5 % faster (a test with 10000 units
where more than 200000 hashmaps are allocated - pure malloc: 449±4 ms,
mempools: 427±7 ms).
Here are some memory usage numbers, taken on my laptop with a more or
less normal Fedora setup after booting with SELinux disabled (SELinux
increases systemd's memory usage significantly):
systemd (PID 1) Original New Change
dirty memory (from pmap -x 1) [KiB] 2152 1264 -41 %
total heap allocations (from gdb-heap) [KiB] 1623 756 -53 %
Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
