Incremental gc, being stateful and not gc-able (ironic), was always
going to need to be conditionally compilable.
This moves incremental gc behind the LFS_GC define, so that we can focus
on the "default" costs. This cuts lfs_t in nearly half!
lfs_t with LFS_GC: 308
lfs_t without LFS_C: 168 (-45.5%)
This does save less code than one might expect though. We still need
most of the internal traversal/gc logic for things like block allocation
and orphan cleanup, so most of the savings is limited to the RAM storing
the incremental state:
code stack ctx
before: 37916 2608 768
after with LFS_CFG: 37944 (+0.1%) 2608 (+0.0%) 768 (+0.0%)
after without LFS_CFG: 37796 (-0.3%) 2608 (+0.0%) 620 (-19.3%)
On the flip side, this does mean most of the incremental gc
functionality is still availables in the lfsr_traversal_t APIs.
Applications with more advanced gc use-cases may actually benefit from
_not_ enabling the incremental gc APIs, and instead use the
lfsr_traversal_t APIs directly.
Christopher Haster
1b3054db89