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lib/uint64set: remove memory allocation in getOrCreateSmallPool()

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This partially reverts fb82c4b9fa

It has been appeared that the additional memory allocation may result in higher GC pauses.
It is better to spend CPU time on copying bigger bucket16 structs instead of increasing query latencies due to higher GC pauses
This commit is contained in:
Aliaksandr Valialkin 2021-04-14 12:27:40 +03:00
parent e5db518c0f
commit 9b1999a5ff
1 changed files with 7 additions and 32 deletions
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39
lib/uint64set/uint64set.go
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@ -707,7 +707,7 @@ const (
type bucket16 struct {
bits *[wordsPerBucket]uint64
smallPool *[smallPoolSize]uint16
smallPool [smallPoolSize]uint16
smallPoolLen int
}
@ -789,9 +789,6 @@ func (b *bucket16) sizeBytes() uint64 {
if b.bits != nil {
n += unsafe.Sizeof(*b.bits)
}
if b.smallPool != nil {
n += unsafe.Sizeof(*b.smallPool)
}
return uint64(n)
}
@ -802,19 +799,8 @@ func (b *bucket16) copyTo(dst *bucket16) {
bits := *b.bits
dst.bits = &bits
}
dst.smallPool = b.smallPool
dst.smallPoolLen = b.smallPoolLen
if b.smallPool != nil {
sp := dst.getOrCreateSmallPool()
*sp = *b.smallPool
}
}
func (b *bucket16) getOrCreateSmallPool() *[smallPoolSize]uint16 {
if b.smallPool == nil {
var sp [smallPoolSize]uint16
b.smallPool = &sp
}
return b.smallPool
}
func (b *bucket16) add(x uint16) bool {
@ -861,7 +847,7 @@ func (b *bucket16) addToSmallPool(x uint16) bool {
if b.hasInSmallPool(x) {
return false
}
sp := b.getOrCreateSmallPool()
sp := b.smallPool[:]
if b.smallPoolLen < len(sp) {
sp[b.smallPoolLen] = x
b.smallPoolLen++
@ -886,11 +872,7 @@ func (b *bucket16) has(x uint16) bool {
}
func (b *bucket16) hasInSmallPool(x uint16) bool {
sp := b.smallPool
if sp == nil {
return false
}
for _, v := range sp[:b.smallPoolLen] {
for _, v := range b.smallPool[:b.smallPoolLen] {
if v == x {
return true
}
@ -910,10 +892,7 @@ func (b *bucket16) del(x uint16) bool {
}
func (b *bucket16) delFromSmallPool(x uint16) bool {
sp := b.smallPool
if sp == nil {
return false
}
sp := b.smallPool[:]
for i, v := range sp[:b.smallPoolLen] {
if v == x {
copy(sp[i:], sp[i+1:])
@ -927,15 +906,11 @@ func (b *bucket16) delFromSmallPool(x uint16) bool {
func (b *bucket16) appendTo(dst []uint64, hi uint32, hi16 uint16) []uint64 {
hi64 := uint64(hi)<<32 | uint64(hi16)<<16
if b.bits == nil {
sp := b.smallPool
if sp == nil {
return dst
}
// Use smallPoolSorter instead of sort.Slice here in order to reduce memory allocations.
sps := smallPoolSorterPool.Get().(*smallPoolSorter)
// Sort a copy of sp, since b must be readonly in order to prevent from data races
// Sort a copy of b.smallPool, since b must be readonly in order to prevent from data races
// when b.appendTo is called from concurrent goroutines.
sps.smallPool = *sp
sps.smallPool = b.smallPool
sps.a = sps.smallPool[:b.smallPoolLen]
if len(sps.a) > 1 && !sort.IsSorted(sps) {
sort.Sort(sps)