runtime: eliminate mheap.busy* lists

The old whole-page reclaimer was the only thing that used the busy
span lists. Remove them so nothing uses them any more.

Change-Id: I4007dd2be08b9ef41bfdb0c387215c73c392cc4c
Reviewed-on: https://go-review.googlesource.com/c/138960
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index 3dd79cfdfeaf1e0b11a585bc190015775420cd76..99994593c3934994f3316912579fbd4fc620899b 100644 (file)
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -30,12 +30,11 @@ const minPhysPageSize = 4096
 //go:notinheap
 type mheap struct {
        lock      mutex
-       free      mTreap    // free and non-scavenged spans
-       scav      mTreap    // free and scavenged spans
-       busy      mSpanList // busy list of spans
-       sweepgen  uint32    // sweep generation, see comment in mspan
-       sweepdone uint32    // all spans are swept
-       sweepers  uint32    // number of active sweepone calls
+       free      mTreap // free and non-scavenged spans
+       scav      mTreap // free and scavenged spans
+       sweepgen  uint32 // sweep generation, see comment in mspan
+       sweepdone uint32 // all spans are swept
+       sweepers  uint32 // number of active sweepone calls
 
        // allspans is a slice of all mspans ever created. Each mspan
        // appears exactly once.
@@ -676,7 +675,7 @@ func (h *mheap) init() {
        h.spanalloc.zero = false
 
        // h->mapcache needs no init
-       h.busy.init()
+
        for i := range h.central {
                h.central[i].mcentral.init(spanClass(i))
        }
@@ -893,8 +892,6 @@ func (h *mheap) alloc_m(npage uintptr, spanclass spanClass, large bool) *mspan {
                        mheap_.largealloc += uint64(s.elemsize)
                        mheap_.nlargealloc++
                        atomic.Xadd64(&memstats.heap_live, int64(npage<<_PageShift))
-                       // Swept spans are at the end of lists.
-                       h.busy.insertBack(s)
                }
        }
        // heap_scan and heap_live were updated.
@@ -1199,9 +1196,6 @@ func (h *mheap) freeSpanLocked(s *mspan, acctinuse, acctidle bool, unusedsince i
                memstats.heap_idle += uint64(s.npages << _PageShift)
        }
        s.state = mSpanFree
-       if s.inList() {
-               h.busy.remove(s)
-       }
 
        // Stamp newly unused spans. The scavenger will use that
        // info to potentially give back some pages to the OS.