I opted to embed the Bitmap structure directly in the ExitStatusSet.
This means that memory usage is a bit higher for units which don't define
this setting:
Service changes:
/* size: 2720, cachelines: 43, members: 73 */
/* sum members: 2680, holes: 9, sum holes: 39 */
/* sum bitfield members: 7 bits, bit holes: 1, sum bit holes: 1 bits */
/* last cacheline: 32 bytes */
/* size: 2816, cachelines: 44, members: 73 */
/* sum members: 2776, holes: 9, sum holes: 39 */
/* sum bitfield members: 7 bits, bit holes: 1, sum bit holes: 1 bits */
But this way the code is simpler and we do less pointer chasing.
This doesn't have much effect on the final build, because we link libbasic.a
into libsystemd-shared.so, so in the end, all the object built from basic/
end up in libsystemd-shared. And when the static library is linked into binaries,
any objects that are included in it but are not used are trimmed. Hence, the
size of output artifacts doesn't change:
$ du -sb /var/tmp/inst*
54181861 /var/tmp/inst1 (old)
54207441 /var/tmp/inst1s (old split-usr)
54182477 /var/tmp/inst2 (new)
54208041 /var/tmp/inst2s (new split-usr)
(The negligible change in size is because libsystemd-shared.so is bigger
by a few hundred bytes. I guess it's because symbols are named differently
or something like that.)
The effect is on the build process, in particular partial builds. This change
effectively moves the requirements on some build steps toward the leaves of the
dependency tree. Two effects:
- when building items that do not depend on libsystemd-shared, we
build less stuff for libbasic.a (which wouldn't be used anyway,
so it's a net win).
- when building items that do depend on libshared, we reduce libbasic.a as a
synchronization point, possibly allowing better parallelism.
Method:
1. copy list of .h files from src/basic/meson.build to /tmp/basic
2. $ for i in $(grep '.h$' /tmp/basic); do echo $i; git --no-pager grep "include \"$i\"" src/basic/ 'src/lib*' 'src/nss-*' 'src/journal/sd-journal.c' |grep -v "${i%.h}.c";echo ;done | less
Yu Watanabe