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| author | Dmitriy Vyukov <dvyukov@google.com> | 2014-08-19 17:38:00 +0400 |
|---|---|---|
| committer | Dmitriy Vyukov <dvyukov@google.com> | 2014-08-19 17:38:00 +0400 |
| commit | ff3fa1b32dba4448bed45282b1038a4f8e9c23dc (patch) | |
| tree | d5c7458bf20b8918dde0750efb67b6d9aaa33026 /src/pkg/runtime/malloc.go | |
| parent | fb44fb6cb7fdadced51db03403b9f5d93fefa5a5 (diff) | |
| download | go-ff3fa1b32dba4448bed45282b1038a4f8e9c23dc.tar.xz | |
runtime: make the GC bitmap a byte array
Half the code in the garbage collector accesses the bitmap
as an array of bytes instead of as an array of uintptrs.
This is tricky to do correctly in a portable fashion,
it breaks on big-endian systems.
Make the bitmap a byte array.
Simplifies markallocated, scanblock and span sweep along the way,
as we don't need to recalculate bitmap position for each word.
LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews, rlh, rsc
https://golang.org/cl/125250043
Diffstat (limited to 'src/pkg/runtime/malloc.go')
| -rw-r--r-- | src/pkg/runtime/malloc.go | 22 |
1 files changed, 7 insertions, 15 deletions
diff --git a/src/pkg/runtime/malloc.go b/src/pkg/runtime/malloc.go index 152b3b6b68..8ee460755f 100644 --- a/src/pkg/runtime/malloc.go +++ b/src/pkg/runtime/malloc.go @@ -22,8 +22,8 @@ const ( pageSize = 1 << pageShift pageMask = pageSize - 1 - wordsPerBitmapWord = ptrSize * 8 / 4 gcBits = 4 + wordsPerBitmapByte = 8 / gcBits bitsPerPointer = 2 bitsMask = 1<<bitsPerPointer - 1 pointersPerByte = 8 / bitsPerPointer @@ -211,8 +211,8 @@ func gomallocgc(size uintptr, typ *_type, flags int) unsafe.Pointer { { arena_start := uintptr(unsafe.Pointer(mheap_.arena_start)) off := (uintptr(x) - arena_start) / ptrSize - xbits := (*uintptr)(unsafe.Pointer(arena_start - off/wordsPerBitmapWord*ptrSize - ptrSize)) - shift := (off % wordsPerBitmapWord) * gcBits + xbits := (*uint8)(unsafe.Pointer(arena_start - off/wordsPerBitmapByte - 1)) + shift := (off % wordsPerBitmapByte) * gcBits if debugMalloc && ((*xbits>>shift)&(bitMask|bitPtrMask)) != bitBoundary { println("runtime: bits =", (*xbits>>shift)&(bitMask|bitPtrMask)) gothrow("bad bits in markallocated") @@ -260,8 +260,7 @@ func gomallocgc(size uintptr, typ *_type, flags int) unsafe.Pointer { ptrmask = (*uint8)(unsafe.Pointer(&typ.gc[0])) // embed mask } if size == 2*ptrSize { - xbitsb := (*uint8)(add(unsafe.Pointer(xbits), shift/8)) - *xbitsb = *ptrmask | bitBoundary + *xbits = *ptrmask | bitBoundary goto marked } te = uintptr(typ.size) / ptrSize @@ -283,19 +282,12 @@ func gomallocgc(size uintptr, typ *_type, flags int) unsafe.Pointer { v &^= uint8(bitPtrMask << 4) } - off := (uintptr(x) + i - arena_start) / ptrSize - xbits := (*uintptr)(unsafe.Pointer(arena_start - off/wordsPerBitmapWord*ptrSize - ptrSize)) - shift := (off % wordsPerBitmapWord) * gcBits - xbitsb := (*uint8)(add(unsafe.Pointer(xbits), shift/8)) - *xbitsb = v + *xbits = v + xbits = (*byte)(add(unsafe.Pointer(xbits), ^uintptr(0))) } if size0%(2*ptrSize) == 0 && size0 < size { // Mark the word after last object's word as bitsDead. - off := (uintptr(x) + size0 - arena_start) / ptrSize - xbits := (*uintptr)(unsafe.Pointer(arena_start - off/wordsPerBitmapWord*ptrSize - ptrSize)) - shift := (off % wordsPerBitmapWord) * gcBits - xbitsb := (*uint8)(add(unsafe.Pointer(xbits), shift/8)) - *xbitsb = bitsDead << 2 + *xbits = bitsDead << 2 } } marked: |