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Use fastRand instead of locked-rand in skiplist (#1173) #1173

Merged
merged 9 commits into from
Jan 14, 2020
Merged

Use fastRand instead of locked-rand in skiplist (#1173) #1173

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9ddb806
Replace global rand lock with local one
Dec 25, 2019
8a97b12
Use rand.Rand instead of rand.Source
Jan 6, 2020
47a95ed
Merge branch 'master' into ibrahim/global-rand-memtable
Jan 7, 2020
5be7f76
Add comment
Jan 8, 2020
c25d2b2
Use fastRand instead of rand.New(..)
Jan 10, 2020
baffaf0
Add Concurrent Write benchmark
Jan 10, 2020
e9dee79
fix table checksum test
Jan 13, 2020
4127cea
Return error instead of assert
Jan 13, 2020
c9ed8f2
fixup
Jan 14, 2020
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9 changes: 6 additions & 3 deletions skl/skl.go
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ import (
"math"
"math/rand"
"sync/atomic"
"time"
"unsafe"

"github.com/dgraph-io/badger/v2/y"
Expand Down Expand Up @@ -79,6 +80,7 @@ type Skiplist struct {
head *node
ref int32
arena *Arena
rand *rand.Rand
}

// IncrRef increases the refcount
Expand Down Expand Up @@ -132,6 +134,7 @@ func NewSkiplist(arenaSize int64) *Skiplist {
head: head,
arena: arena,
ref: 1,
rand: rand.New(rand.NewSource(time.Now().UnixNano())),
}
}

Expand Down Expand Up @@ -165,9 +168,9 @@ func (s *node) casNextOffset(h int, old, val uint32) bool {
// return n != nil && y.CompareKeys(key, n.key) > 0
//}

func randomHeight() int {
func (s *Skiplist) randomHeight() int {
h := 1
for h < maxHeight && rand.Uint32() <= heightIncrease {
for h < maxHeight && s.rand.Uint32() <= heightIncrease {
h++
}
return h
Expand Down Expand Up @@ -300,7 +303,7 @@ func (s *Skiplist) Put(key []byte, v y.ValueStruct) {
}

// We do need to create a new node.
height := randomHeight()
height := s.randomHeight()
x := newNode(s.arena, key, v, height)

// Try to increase s.height via CAS.
Expand Down