[dev.garbage] Merge remote-tracking branch 'origin/master' into HEAD

[gostls13.git] / src / runtime / mheap.go

diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index 9f07dfbb995a032ba48c25070d9e8a9a94ef4d5b..1333dd696bbaa5a6949cf3e76719e9224cfac53c 100644 (file)
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -870,15 +870,6 @@ func (h *mheap) busyList(npages uintptr) *mSpanList {
 }
 
 func scavengelist(list *mSpanList, now, limit uint64) uintptr {
-       if sys.PhysPageSize > _PageSize {
-               // golang.org/issue/9993
-               // If the physical page size of the machine is larger than
-               // our logical heap page size the kernel may round up the
-               // amount to be freed to its page size and corrupt the heap
-               // pages surrounding the unused block.
-               return 0
-       }
-
        if list.isEmpty() {
                return 0
        }
@@ -886,11 +877,30 @@ func scavengelist(list *mSpanList, now, limit uint64) uintptr {
        var sumreleased uintptr
        for s := list.first; s != nil; s = s.next {
                if (now-uint64(s.unusedsince)) > limit && s.npreleased != s.npages {
-                       released := (s.npages - s.npreleased) << _PageShift
+                       start := uintptr(s.start) << _PageShift
+                       end := start + s.npages<<_PageShift
+                       if sys.PhysPageSize > _PageSize {
+                               // We can only release pages in
+                               // PhysPageSize blocks, so round start
+                               // and end in. (Otherwise, madvise
+                               // will round them *out* and release
+                               // more memory than we want.)
+                               start = (start + sys.PhysPageSize - 1) &^ (sys.PhysPageSize - 1)
+                               end &^= sys.PhysPageSize - 1
+                               if start == end {
+                                       continue
+                               }
+                       }
+                       len := end - start
+
+                       released := len - (s.npreleased << _PageShift)
+                       if sys.PhysPageSize > _PageSize && released == 0 {
+                               continue
+                       }
                        memstats.heap_released += uint64(released)
                        sumreleased += released
-                       s.npreleased = s.npages
-                       sysUnused(unsafe.Pointer(s.start<<_PageShift), s.npages<<_PageShift)
+                       s.npreleased = len >> _PageShift
+                       sysUnused(unsafe.Pointer(start), len)
                }
        }
        return sumreleased