Add accounting allocator and native memory pressure C-API#244
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Add a process-wide allocation counter and threshold-crossing notification
that the managed SkiaSharp layer uses to drive GC.AddMemoryPressure /
RemoveMemoryPressure without polling.
The bookkeeping (atomic counter, threshold watermark, CAS-claimed
crossing logic, malloc_usable_size dispatching, public C-API) lives in
a dedicated src/c/sk_memory.cpp / include/c/sk_memory.h pair in the
SkiaSharp C shim. The upstream allocator
(src/ports/SkMemory_malloc.cpp) gains only a forward declaration of
two extern "C" hook functions and a single call site in each of
sk_malloc_flags / sk_free / sk_realloc_throw -- ~25 added lines total,
no upstream lines removed.
The new public C-API:
uint64_t sk_memory_get_native_allocated(void);
void sk_memory_set_threshold_callback(
sk_memory_threshold_proc callback,
uint64_t threshold_bytes);
A NULL callback or zero threshold disables notifications; the counter
keeps updating.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Description of Change
Add src/c/sk_memory_skiasharp.cpp, an accounting variant of src/ports/SkMemory_malloc.cpp. Behaviorally identical to the upstream allocator, but every successful sk_malloc/sk_realloc/sk_free updates an atomic int64 counter (measured via malloc_usable_size / _msize / malloc_size). A registered callback fires whenever the counter drifts +/- threshold bytes since the last notification, claimed via CAS so only one thread fires per crossing.
Expose two new functions in include/c/sk_graphics.h:
uint64_t sk_graphics_get_native_memory_allocated(void);
void sk_graphics_set_native_memory_threshold_callback(
sk_native_memory_threshold_proc callback,
uint64_t threshold_bytes);
BUILD.gn: link the SkiaSharp variant instead of the upstream allocator. The sksl tool's separate build (gn/sksl.gni) keeps the default malloc.
Lets the managed layer report Skia's native byte usage to the GC via GC.AddMemoryPressure / RemoveMemoryPressure without polling.
SkiaSharp Issue
Related to mono/SkiaSharp#1288
API Changes
uint64_t sk_graphics_get_native_memory_allocated(void);
void sk_graphics_set_native_memory_threshold_callback(
sk_native_memory_threshold_proc callback,
uint64_t threshold_bytes);
Behavioral Changes
None.
Required SkiaSharp PR
Requires mono/SkiaSharp#4067
PR Checklist
skiasharpat time of PR