When an array element is added or removed, make only the relevant page
writable, rather than the entire array. The entire array is still made
writable during recompaction and expansion.
This change fixes most of a large regression in __cxa_atexit runtime
(blueline, taskset 10, performance governor, 100000 registrations,
times are in seconds)
- Q: _Exit=0.292380, exit=0.626801
- R: _Exit=28.435082, exit=95.785110
- new: _Exit=0.352285, exit=0.713893
Test: bionic unit tests
Test: adb shell taskset 10 \
/data/benchmarktest64/bionic-spawn-benchmarks/bionic-spawn-benchmarks \
--benchmark_filter='atexit' \
--benchmark_display_aggregates_only=true \
--benchmark_repetitions=10
Bug: http://b/168043760
Change-Id: I88cc15c29c9890b422b7f621f29f98a03ca1f886
Simplify:
- Use a single memory-mapped region to hold the table of destructors.
Double its capacity each time it is expanded.
- Add a recompaction pass at the end of __cxa_finalize that shifts
entries forward and uses madvise to clean pages.
Bug: http://b/148055738
Test: bionic-unit-tests
Change-Id: Ieb9da2b88640a8a5277d217b43826b5b7e246781
