From: Josh Bleecher Snyder <josharian@gmail.com>
Date: Tue, 19 Apr 2016 22:14:26 +0000 (-0700)
Subject: runtime: call mallocgc directly from makeslice and growslice
X-Git-Tag: go1.7beta1~593
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=0150f15a924a7b4ac0c794012f6b12c8aa406b54;p=gostls13.git

runtime: call mallocgc directly from makeslice and growslice

The extra checks provided by newarray are
redundant in these cases.

This shrinks by one frame the call stack expected
by the pprof test.

name                      old time/op  new time/op  delta
MakeSlice-8               34.3ns ± 2%  30.5ns ± 3%  -11.03%  (p=0.000 n=24+22)
GrowSlicePtr-8             134ns ± 2%   129ns ± 3%   -3.25%  (p=0.000 n=25+24)

Change-Id: Icd828655906b921c732701fd9d61da3fa217b0af
Reviewed-on: https://go-review.googlesource.com/22276
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
---

diff --git a/src/runtime/pprof/mprof_test.go b/src/runtime/pprof/mprof_test.go
index d15102c703..0fff9d46d9 100644
--- a/src/runtime/pprof/mprof_test.go
+++ b/src/runtime/pprof/mprof_test.go
@@ -82,7 +82,7 @@ func TestMemoryProfiler(t *testing.T) {
 #	0x[0-9,a-f]+	runtime/pprof_test\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:61
 `, (1<<10)*memoryProfilerRun, (1<<20)*memoryProfilerRun),
 
-		fmt.Sprintf(`0: 0 \[%v: %v\] @ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+
+		fmt.Sprintf(`0: 0 \[%v: %v\] @ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+
 #	0x[0-9,a-f]+	runtime/pprof_test\.allocateTransient2M\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:27
 #	0x[0-9,a-f]+	runtime/pprof_test\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:62
 `, memoryProfilerRun, (2<<20)*memoryProfilerRun),
diff --git a/src/runtime/slice.go b/src/runtime/slice.go
index f9414d7658..873e97ebff 100644
--- a/src/runtime/slice.go
+++ b/src/runtime/slice.go
@@ -55,7 +55,12 @@ func makeslice(t *slicetype, len64, cap64 int64) slice {
 		panic(errorString("makeslice: cap out of range"))
 	}
 
-	p := newarray(t.elem, uintptr(cap))
+	et := t.elem
+	var flags uint32
+	if et.kind&kindNoPointers != 0 {
+		flags = flagNoScan
+	}
+	p := mallocgc(et.size*uintptr(cap), et, flags)
 	return slice{p, len, cap}
 }
 
@@ -130,7 +135,7 @@ func growslice(t *slicetype, old slice, cap int) slice {
 		memclr(add(p, lenmem), capmem-lenmem)
 	} else {
 		// Note: can't use rawmem (which avoids zeroing of memory), because then GC can scan uninitialized memory.
-		p = newarray(et, uintptr(newcap))
+		p = mallocgc(capmem, et, 0)
 		if !writeBarrier.enabled {
 			memmove(p, old.array, lenmem)
 		} else {