runtime: make nlargealloc and largealloc mcache fields

This change makes nlargealloc and largealloc into mcache fields just
like nlargefree and largefree. These local fields become the new
source-of-truth. This change also moves the accounting for these fields
out of allocSpan (which is an inappropriate place for it -- this
accounting generally happens much closer to the point of allocation) and
into largeAlloc. This move is partially possible now that we can call
gcController.revise at that point.

Furthermore, this change moves largeAlloc into mcache.go and makes it a
method of mcache. While there's a little bit of a mismatch here because
largeAlloc barely interacts with the mcache, it helps solidify the
mcache as the first allocation layer and provides a clear place to
aggregate and manage statistics.

Change-Id: I37b5e648710733bb4c04430b71e96700e438587a
Reviewed-on: https://go-review.googlesource.com/c/go/+/246965
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>

1 files changed, 1 insertions, 32 deletions

diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index b19d1f2671..ec601ccb39 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -1082,9 +1082,7 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
 		}
 	} else {
 		shouldhelpgc = true
-		systemstack(func() {
-			span = largeAlloc(size, needzero, noscan)
-		})
+		span = c.largeAlloc(size, needzero, noscan)
 		span.freeindex = 1
 		span.allocCount = 1
 		x = unsafe.Pointer(span.base())
@@ -1179,35 +1177,6 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
 	return x
 }
 
-func largeAlloc(size uintptr, needzero bool, noscan bool) *mspan {
-	// print("largeAlloc size=", size, "\n")
-
-	if size+_PageSize < size {
-		throw("out of memory")
-	}
-	npages := size >> _PageShift
-	if size&_PageMask != 0 {
-		npages++
-	}
-
-	// Deduct credit for this span allocation and sweep if
-	// necessary. mHeap_Alloc will also sweep npages, so this only
-	// pays the debt down to npage pages.
-	deductSweepCredit(npages*_PageSize, npages)
-
-	spc := makeSpanClass(0, noscan)
-	s := mheap_.alloc(npages, spc, needzero)
-	if s == nil {
-		throw("out of memory")
-	}
-	// Put the large span in the mcentral swept list so that it's
-	// visible to the background sweeper.
-	mheap_.central[spc].mcentral.fullSwept(mheap_.sweepgen).push(s)
-	s.limit = s.base() + size
-	heapBitsForAddr(s.base()).initSpan(s)
-	return s
-}
-
 // implementation of new builtin
 // compiler (both frontend and SSA backend) knows the signature
 // of this function