From 7f574e476ac4a6e8c2719b9674ee7b3786bb8401 Mon Sep 17 00:00:00 2001
From: Michael Anthony Knyszek <mknyszek@google.com>
Date: Wed, 18 Sep 2019 15:15:59 +0000
Subject: [PATCH] runtime: remove unnecessary large parameter to mheap_.alloc

mheap_.alloc currently accepts both a spanClass and a "large" parameter
indicating whether the allocation is large. These are redundant, since
spanClass.sizeclass() == 0 is an equivalent way to determine this and is
already used in mheap_.alloc. There are no places in the runtime where
the size class could be non-zero and large == true.

Updates #35112.

Change-Id: Ie66facf8f0faca6f4cd3d20a8ac4bc259e11823d
Reviewed-on: https://go-review.googlesource.com/c/go/+/196639
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
---
 src/runtime/malloc.go   |  2 +-
 src/runtime/mcentral.go |  2 +-
 src/runtime/mheap.go    | 21 ++++++++++-----------
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 3e86f9f64de213..39c5fa2a25782c 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -1149,7 +1149,7 @@ func largeAlloc(size uintptr, needzero bool, noscan bool) *mspan {
 	// pays the debt down to npage pages.
 	deductSweepCredit(npages*_PageSize, npages)
 
-	s := mheap_.alloc(npages, makeSpanClass(0, noscan), true, needzero)
+	s := mheap_.alloc(npages, makeSpanClass(0, noscan), needzero)
 	if s == nil {
 		throw("out of memory")
 	}
diff --git a/src/runtime/mcentral.go b/src/runtime/mcentral.go
index 2f97b7d0946bd5..78a3ae6ac1960d 100644
--- a/src/runtime/mcentral.go
+++ b/src/runtime/mcentral.go
@@ -252,7 +252,7 @@ func (c *mcentral) grow() *mspan {
 	npages := uintptr(class_to_allocnpages[c.spanclass.sizeclass()])
 	size := uintptr(class_to_size[c.spanclass.sizeclass()])
 
-	s := mheap_.alloc(npages, c.spanclass, false, true)
+	s := mheap_.alloc(npages, c.spanclass, true)
 	if s == nil {
 		return nil
 	}
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index 726d93dcb989ec..72702534d98ed6 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -854,7 +854,7 @@ func (h *mheap) reclaimChunk(arenas []arenaIdx, pageIdx, n uintptr) uintptr {
 // any stack growth during alloc_m would self-deadlock.
 //
 //go:systemstack
-func (h *mheap) alloc_m(npage uintptr, spanclass spanClass, large bool) *mspan {
+func (h *mheap) alloc_m(npage uintptr, spanclass spanClass) *mspan {
 	_g_ := getg()
 
 	// To prevent excessive heap growth, before allocating n pages
@@ -901,6 +901,11 @@ func (h *mheap) alloc_m(npage uintptr, spanclass spanClass, large bool) *mspan {
 			s.divMul = 0
 			s.divShift2 = 0
 			s.baseMask = 0
+
+			// Update additional stats.
+			mheap_.largealloc += uint64(s.elemsize)
+			mheap_.nlargealloc++
+			atomic.Xadd64(&memstats.heap_live, int64(npage<<_PageShift))
 		} else {
 			m := &class_to_divmagic[sizeclass]
 			s.divShift = m.shift
@@ -932,13 +937,8 @@ func (h *mheap) alloc_m(npage uintptr, spanclass spanClass, large bool) *mspan {
 		arena, pageIdx, pageMask := pageIndexOf(s.base())
 		arena.pageInUse[pageIdx] |= pageMask
 
-		// update stats, sweep lists
+		// Update related page sweeper stats.
 		h.pagesInUse += uint64(npage)
-		if large {
-			mheap_.largealloc += uint64(s.elemsize)
-			mheap_.nlargealloc++
-			atomic.Xadd64(&memstats.heap_live, int64(npage<<_PageShift))
-		}
 	}
 	// heap_scan and heap_live were updated.
 	if gcBlackenEnabled != 0 {
@@ -964,17 +964,16 @@ func (h *mheap) alloc_m(npage uintptr, spanclass spanClass, large bool) *mspan {
 
 // alloc allocates a new span of npage pages from the GC'd heap.
 //
-// Either large must be true or spanclass must indicates the span's
-// size class and scannability.
+// spanclass indicates the span's size class and scannability.
 //
 // If needzero is true, the memory for the returned span will be zeroed.
-func (h *mheap) alloc(npage uintptr, spanclass spanClass, large bool, needzero bool) *mspan {
+func (h *mheap) alloc(npage uintptr, spanclass spanClass, needzero bool) *mspan {
 	// Don't do any operations that lock the heap on the G stack.
 	// It might trigger stack growth, and the stack growth code needs
 	// to be able to allocate heap.
 	var s *mspan
 	systemstack(func() {
-		s = h.alloc_m(npage, spanclass, large)
+		s = h.alloc_m(npage, spanclass)
 	})
 
 	if s != nil {