[dev.garbage] runtime: Turn concurrent GC on by default. Avoid write barriers for GC internal structures such as free lists.
LGTM=rsc
R=rsc
CC=golang-codereviews, rsc
https://golang.org/cl/179000043
diff --git a/src/runtime/mcentral.go b/src/runtime/mcentral.go
index 0d172a0..ae5c6f1 100644
--- a/src/runtime/mcentral.go
+++ b/src/runtime/mcentral.go
@@ -55,7 +55,7 @@
mSpanList_InsertBack(&c.empty, s)
unlock(&c.lock)
mSpan_Sweep(s, true)
- if s.freelist != nil {
+ if s.freelist.ptr() != nil {
goto havespan
}
lock(&c.lock)
@@ -90,7 +90,7 @@
if n == 0 {
gothrow("empty span")
}
- if s.freelist == nil {
+ if s.freelist.ptr() == nil {
gothrow("freelist empty")
}
s.incache = true
@@ -122,14 +122,14 @@
// the latest generation.
// If preserve=true, don't return the span to heap nor relink in MCentral lists;
// caller takes care of it.
-func mCentral_FreeSpan(c *mcentral, s *mspan, n int32, start *mlink, end *mlink, preserve bool) bool {
+func mCentral_FreeSpan(c *mcentral, s *mspan, n int32, start gclinkptr, end gclinkptr, preserve bool) bool {
if s.incache {
gothrow("freespan into cached span")
}
// Add the objects back to s's free list.
- wasempty := s.freelist == nil
- end.next = s.freelist
+ wasempty := s.freelist.ptr() == nil
+ end.ptr().next = s.freelist
s.freelist = start
s.ref -= uint16(n)
@@ -165,7 +165,7 @@
// s is completely freed, return it to the heap.
mSpanList_Remove(s)
s.needzero = 1
- s.freelist = nil
+ s.freelist = 0
unlock(&c.lock)
unmarkspan(uintptr(s.start)<<_PageShift, s.npages<<_PageShift)
mHeap_Free(&mheap_, s, 0)
@@ -183,17 +183,21 @@
return nil
}
- // Carve span into sequence of blocks.
- tailp := &s.freelist
p := uintptr(s.start << _PageShift)
s.limit = p + size*n
- for i := uintptr(0); i < n; i++ {
- v := (*mlink)(unsafe.Pointer(p))
- *tailp = v
- tailp = &v.next
+ head := gclinkptr(p)
+ tail := gclinkptr(p)
+ // i==0 iteration already done
+ for i := uintptr(1); i < n; i++ {
p += size
+ tail.ptr().next = gclinkptr(p)
+ tail = gclinkptr(p)
}
- *tailp = nil
+ if s.freelist.ptr() != nil {
+ gothrow("freelist not empty")
+ }
+ tail.ptr().next = 0
+ s.freelist = head
markspan(unsafe.Pointer(uintptr(s.start)<<_PageShift), size, n, size*n < s.npages<<_PageShift)
return s
}
