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Revert "runtime: redo heap bitmap"

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This reverts commit b589208c8c.

Reason for revert: Bug somewhere in this code, causing wasm and maybe linux/386 to fail.

Change-Id: I5e1e501d839584e0219271bb937e94348f83c11f
Reviewed-on: https://go-review.googlesource.com/c/go/+/422395
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Keith Randall <khr@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Keith Randall 2022-08-09 15:44:48 +00:00
parent e1a8e0e05d
commit ad0287f496
12 changed files with 1126 additions and 530 deletions
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19
src/runtime/mheap.go
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@ -221,22 +221,9 @@ var mheap_ mheap
//go:notinheap
type heapArena 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
// this arena. See mbitmap.go for a description. Use the
// heapBits type to access this.
bitmap [heapArenaBitmapBytes]byte
// spans maps from virtual address page ID within this arena to *mspan.
// For allocated spans, their pages map to the span itself.