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[libpas] jit_heap should support the segregated heap
https://bugs.webkit.org/show_bug.cgi?id=235497
Reviewed by Yusuke Suzuki.
Source/bmalloc:
One of the things that libpas provides is a fast implementation of executable memory allocation, which
libpas calls "jit_heap". The initial implementation of this only used libpas's bitfit and large
algorithms. Bitfit was used for smaller objects and large was used for larger objects. The libpas
segregated heap was disabled in jit_heap. This made sense because:
- Bitfit and large support the shrink() call, where we shrink an allocation in-place. Executable
allocation supports this to aid branch compaction (we compact code after we copy it into its final
resting place, which is after we allocate the memory - so after we finish compaction, we can only
shrink the allocation in-place or not at all).
- Segregated heaps have some virtual address space overheads, and memory overheads, that the bitfit
and large heaps don't have. This happens because segreated heaps will dedicate each page to objects
of exactly one size forever.
However, segregated heaps are substantially faster than bitfit heaps. They are faster under serial
allocation thanks to the fact that no locks need to be acquired for a typical allocation or
deallocation. They are even more faster under parallel allocation thanks to thread-local caching.
This patch enables segregated heaps for the smallest jit_heap allocations (<=2000 bytes). The cutoff
threshold is runtime configurable, so it's possible to disable segregated heaps at runtime by setting
the cutoff to 0.
With the 2000 threshold, this appears to be a 0.3% Speedometer2 speed-up.
While there is a theoretical possibility of memory overhead, I haven't seen it. If we are using jump
islands then the virtual memory overhead of segregated heaps will just mean that we use jump islands
more frequently, which would manifest as a performance regression -- but I've not seen any such
regression. So, this disables the segregated heap if the JIT pool size is too small (see changes to
ExecutableAllocator.cpp in JSC).
- libpas/libpas.xcodeproj/project.pbxproj:
- libpas/src/libpas/jit_heap.c:
(jit_heap_shrink):
- libpas/src/libpas/jit_heap_config.c:
(jit_small_segregated_allocate_page):
(jit_small_segregated_create_page_header):
(jit_small_destroy_page_header):
(jit_small_segregated_shared_page_directory_selector):
(jit_small_bitfit_allocate_page):
(jit_small_bitfit_create_page_header):
(jit_medium_bitfit_create_page_header):
(jit_medium_destroy_page_header):
(jit_prepare_to_enumerate):
(jit_small_bitfit_destroy_page_header): Deleted.
(jit_medium_bitfit_destroy_page_header): Deleted.
- libpas/src/libpas/jit_heap_config.h:
(jit_small_page_header_for_boundary):
(jit_small_boundary_for_page_header):
(jit_medium_page_header_for_boundary):
(jit_medium_boundary_for_page_header):
(jit_heap_config_page_header):
(jit_small_bitfit_page_header_for_boundary): Deleted.
(jit_small_bitfit_boundary_for_page_header): Deleted.
(jit_medium_bitfit_page_header_for_boundary): Deleted.
(jit_medium_bitfit_boundary_for_page_header): Deleted.
- libpas/src/libpas/jit_heap_config_root_data.h:
- libpas/src/libpas/pas_bitfit_heap.c:
(pas_bitfit_heap_select_variant):
(pas_bitfit_heap_construct_and_insert_size_class):
- libpas/src/libpas/pas_bitfit_heap.h:
- libpas/src/libpas/pas_bitfit_page_config.h:
(pas_bitfit_page_config_is_enabled):
- libpas/src/libpas/pas_heap_config.h:
(pas_heap_config_segregated_heap_min_align_shift):
(pas_heap_config_segregated_heap_min_align):
- libpas/src/libpas/pas_segregated_heap.c:
(min_align_for_heap):
(min_object_size_for_heap):
(max_segregated_object_size_for_heap):
(max_bitfit_object_size_for_heap):
(max_object_size_for_heap):
(pas_segregated_heap_ensure_allocator_index):
(pas_segregated_heap_ensure_size_directory_for_size):
(min_object_size_for_heap_config): Deleted.
(max_segregated_object_size_for_heap_config): Deleted.
(max_bitfit_object_size_for_heap_config): Deleted.
(max_object_size_for_heap_config): Deleted.
- libpas/src/libpas/pas_segregated_heap.h:
(pas_segregated_heap_index_for_size):
(pas_segregated_heap_size_for_index):
- libpas/src/libpas/pas_segregated_page.c:
(pas_segregated_page_construct):
- libpas/src/libpas/pas_segregated_page_config.h:
(pas_segregated_page_config_is_enabled):
- libpas/src/libpas/pas_segregated_page_config_kind.def:
- libpas/src/libpas/pas_segregated_page_config_kind_and_role.h:
- libpas/src/libpas/pas_segregated_size_directory.c:
(pas_segregated_size_directory_create):
- libpas/src/test/IsoHeapChaosTests.cpp:
(std::addAllTests):
- libpas/src/test/JITHeapTests.cpp:
(std::testAllocationSize):
(addJITHeapTests):
- libpas/src/test/TestHarness.cpp:
(main):
- libpas/src/test/ViewCacheTests.cpp: Added.
(std::setupConfig):
(std::testDisableViewCacheUsingBoundForNoViewCache):
(std::testEnableViewCacheAtSomeBoundForNoViewCache):
(addViewCacheTests):
Source/JavaScriptCore:
Disable the jit_heap segregated heap if the executable pool size is too small.
- jit/ExecutableAllocator.cpp:
(JSC::initializeJITPageReservation):
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