)
// A generic linked list of blocks. (Typically the block is bigger than sizeof(MLink).)
+// Since assignments to mlink.next will result in a write barrier being preformed
+// this can not be used by some of the internal GC structures. For example when
+// the sweeper is placing an unmarked object on the free list it does not want the
+// write barrier to be called since that could result in the object being reachable.
type mlink struct {
next *mlink
}
+// A gclink is a node in a linked list of blocks, like mlink,
+// but it is opaque to the garbage collector.
+// The GC does not trace the pointers during collection,
+// and the compiler does not emit write barriers for assignments
+// of gclinkptr values. Code should store references to gclinks
+// as gclinkptr, not as *gclink.
+type gclink struct {
+ next gclinkptr
+}
+
+// A gclinkptr is a pointer to a gclink, but it is opaque
+// to the garbage collector.
+type gclinkptr uintptr
+
+// ptr returns the *gclink form of p.
+// The result should be used for accessing fields, not stored
+// in other data structures.
+func (p gclinkptr) ptr() *gclink {
+ return (*gclink)(unsafe.Pointer(p))
+}
+
// sysAlloc obtains a large chunk of zeroed memory from the
// operating system, typically on the order of a hundred kilobytes
// or a megabyte.
}
type stackfreelist struct {
- list *mlink // linked list of free stacks
- size uintptr // total size of stacks in list
+ list gclinkptr // linked list of free stacks
+ size uintptr // total size of stacks in list
}
// Per-thread (in Go, per-P) cache for small objects.
sudogcache *sudog
- gcworkbuf unsafe.Pointer
-
// Local allocator stats, flushed during GC.
local_nlookup uintptr // number of pointer lookups
local_largefree uintptr // bytes freed for large objects (>maxsmallsize)
)
type mspan struct {
- next *mspan // in a span linked list
- prev *mspan // in a span linked list
- start pageID // starting page number
- npages uintptr // number of pages in span
- freelist *mlink // list of free objects
+ next *mspan // in a span linked list
+ prev *mspan // in a span linked list
+ start pageID // starting page number
+ npages uintptr // number of pages in span
+ freelist gclinkptr // list of free objects
// sweep generation:
// if sweepgen == h->sweepgen - 2, the span needs sweeping
// if sweepgen == h->sweepgen - 1, the span is currently being swept