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runtime: fix stale comments about mheap and mspan 

As of 07e738e all spans are allocated out of a treap, and not just
large spans or spans for large objects. Also, now we have a separate
treap for spans that have been scavenged.

Change-Id: I9c2cb7b6798fc536bbd34835da2e888224fd7ed4
Reviewed-on: https://go-review.googlesource.com/c/142958
Reviewed-by: Austin Clements <austin@google.com>
This commit is contained in:
Michael Anthony Knyszek 2018-10-17 20:16:45 +00:00 committed by Michael Knyszek
parent e72595ee0f
commit 2ae8bf7054
1 changed files with 8 additions and 7 deletions
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15
src/runtime/mheap.go
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@ -21,7 +21,7 @@ import (
const minPhysPageSize = 4096
// Main malloc heap.
// The heap itself is the "free[]" and "large" arrays,
// The heap itself is the "free" and "scav" treaps,
// but all the other global data is here too.
//
// mheap must not be heap-allocated because it contains mSpanLists,
@ -147,7 +147,7 @@ type mheap struct {
spanalloc fixalloc // allocator for span*
cachealloc fixalloc // allocator for mcache*
treapalloc fixalloc // allocator for treapNodes* used by large objects
treapalloc fixalloc // allocator for treapNodes*
specialfinalizeralloc fixalloc // allocator for specialfinalizer*
specialprofilealloc fixalloc // allocator for specialprofile*
speciallock mutex // lock for special record allocators.
@ -198,15 +198,16 @@ type arenaHint struct {
// An MSpan is a run of pages.
//
// When a MSpan is in the heap free list, state == mSpanFree
// When a MSpan is in the heap free treap, state == mSpanFree
// and heapmap(s->start) == span, heapmap(s->start+s->npages-1) == span.
// If the MSpan is in the heap scav treap, then in addition to the
// above scavenged == true. scavenged == false in all other cases.
//
// When a MSpan is allocated, state == mSpanInUse or mSpanManual
// and heapmap(i) == span for all s->start <= i < s->start+s->npages.
// Every MSpan is in one doubly-linked list,
// either one of the MHeap's free lists or one of the
// MCentral's span lists.
// Every MSpan is in one doubly-linked list, either in the MHeap's
// busy list or one of the MCentral's span lists.
// An MSpan representing actual memory has state mSpanInUse,
// mSpanManual, or mSpanFree. Transitions between these states are
@ -848,7 +849,7 @@ func (h *mheap) setSpans(base, npage uintptr, s *mspan) {
// Allocates a span of the given size. h must be locked.
// The returned span has been removed from the
// free list, but its state is still mSpanFree.
// free structures, but its state is still mSpanFree.
func (h *mheap) allocSpanLocked(npage uintptr, stat *uint64) *mspan {
var s *mspan