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cmd/gc: allocate non-escaping maps on stack

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Extend escape analysis to make(map[k]v).
If it does not escape, allocate temp buffer for hmap and one bucket on stack.

There are 75 cases of non-escaping maps in std lib.

benchmark                                    old allocs     new allocs     delta
BenchmarkConcurrentStmtQuery                 16161          15161          -6.19%
BenchmarkConcurrentTxQuery                   17658          16658          -5.66%
BenchmarkConcurrentTxStmtQuery               16157          15156          -6.20%
BenchmarkConcurrentRandom                    13637          13114          -3.84%
BenchmarkManyConcurrentQueries               22             20             -9.09%
BenchmarkDecodeComplex128Slice               250            188            -24.80%
BenchmarkDecodeFloat64Slice                  250            188            -24.80%
BenchmarkDecodeInt32Slice                    250            188            -24.80%
BenchmarkDecodeStringSlice                   2250           2188           -2.76%
BenchmarkNewEmptyMap                         1              0              -100.00%
BenchmarkNewSmallMap                         2              0              -100.00%

benchmark                old ns/op     new ns/op     delta
BenchmarkNewEmptyMap     124           55.7          -55.08%
BenchmarkNewSmallMap     317           148           -53.31%

benchmark                old allocs     new allocs     delta
BenchmarkNewEmptyMap     1              0              -100.00%
BenchmarkNewSmallMap     2              0              -100.00%

benchmark                old bytes     new bytes     delta
BenchmarkNewEmptyMap     48            0             -100.00%
BenchmarkNewSmallMap     192           0             -100.00%

Fixes #5449

Change-Id: I24fa66f949d2f138885d9e66a0d160240dc9e8fa
Reviewed-on: https://go-review.googlesource.com/3508
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
This commit is contained in:
Dmitry Vyukov 2015-01-29 19:40:02 +03:00
parent aed88be021
commit b3be360f16
12 changed files with 178 additions and 168 deletions
Download patch file Download diff file Expand all files Collapse all files

16
src/runtime/hashmap.go
View file

@ -182,8 +182,14 @@ func (h *hmap) createOverflow() {
}
}
func makemap(t *maptype, hint int64) *hmap {
// makemap implements a Go map creation make(map[k]v, hint)
// If the compiler has determined that the map or the first bucket
// can be created on the stack, h and/or bucket may be non-nil.
// If h != nil, the map can be created directly in h.
// If bucket != nil, bucket can be used as the first bucket.
func makemap(t *maptype, hint int64, h *hmap, bucket unsafe.Pointer) *hmap {
if sz := unsafe.Sizeof(hmap{}); sz > 48 || sz != uintptr(t.hmap.size) {
println("runtime: sizeof(hmap) =", sz, ", t.hmap.size =", t.hmap.size)
throw("bad hmap size")
}
@ -238,7 +244,7 @@ func makemap(t *maptype, hint int64) *hmap {
// allocate initial hash table
// if B == 0, the buckets field is allocated lazily later (in mapassign)
// If hint is large zeroing this memory could take a while.
var buckets unsafe.Pointer
buckets := bucket
if B != 0 {
if checkgc {
memstats.next_gc = memstats.heap_alloc
@ -250,7 +256,9 @@ func makemap(t *maptype, hint int64) *hmap {
if checkgc {
memstats.next_gc = memstats.heap_alloc
}
h := (*hmap)(newobject(t.hmap))
if h == nil {
h = (*hmap)(newobject(t.hmap))
}
h.count = 0
h.B = B
h.flags = 0
@ -956,7 +964,7 @@ func ismapkey(t *_type) bool {
//go:linkname reflect_makemap reflect.makemap
func reflect_makemap(t *maptype) *hmap {
return makemap(t, 0)
return makemap(t, 0, nil, nil)
}
//go:linkname reflect_mapaccess reflect.mapaccess