diff options
Diffstat (limited to 'src/runtime/mbitmap.go')
| -rw-r--r-- | src/runtime/mbitmap.go | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go index 20323ff82d..e918b3d489 100644 --- a/src/runtime/mbitmap.go +++ b/src/runtime/mbitmap.go @@ -46,6 +46,27 @@ import ( "unsafe" ) +// heapArenaPtrScalar contains the per-heapArena pointer/scalar metadata for the GC. +type heapArenaPtrScalar struct { + // bitmap stores the pointer/scalar bitmap for the words in + // this arena. See mbitmap.go for a description. + // This array uses 1 bit per word of heap, or 1.6% of the heap size (for 64-bit). + bitmap [heapArenaBitmapWords]uintptr + + // If the ith bit of noMorePtrs is true, then there are no more + // pointers for the object containing the word described by the + // high bit of bitmap[i]. + // In that case, bitmap[i+1], ... must be zero until the start + // of the next object. + // We never operate on these entries using bit-parallel techniques, + // so it is ok if they are small. Also, they can't be bigger than + // uint16 because at that size a single noMorePtrs entry + // represents 8K of memory, the minimum size of a span. Any larger + // and we'd have to worry about concurrent updates. + // This array uses 1 bit per word of bitmap, or .024% of the heap size (for 64-bit). + noMorePtrs [heapArenaBitmapWords / 8]uint8 +} + // addb returns the byte pointer p+n. // //go:nowritebarrier |