mvcc: cache consistentIndex
Called on every entry apply and boltdb requests aren't free.
@@ -19,6 +19,7 @@ import (
"errors"
"math"
"sync"
+ "sync/atomic"
"time"
"github.com/coreos/etcd/lease"
@@ -67,6 +68,10 @@ type store struct {
ReadView
WriteView
+ // consistentIndex caches the "consistent_index" key's value. Accessed
+ // through atomics so must be 64-bit aligned.
+ consistentIndex uint64
+
// mu read locks for txns and write locks for non-txn store changes.
mu sync.RWMutex
@@ -234,6 +239,7 @@ func (s *store) Restore(b backend.Backend) error {
close(s.stopc)
s.fifoSched.Stop()
+ atomic.StoreUint64(&s.consistentIndex, 0)
s.b = b
s.kvindex = newTreeIndex()
s.currentRev = 1
@@ -380,14 +386,18 @@ func (s *store) saveIndex(tx backend.BatchTx) {
return
}
bs := s.bytesBuf8
- binary.BigEndian.PutUint64(bs, s.ig.ConsistentIndex())
+ ci := s.ig.ConsistentIndex()
+ binary.BigEndian.PutUint64(bs, ci)
// put the index into the underlying backend
// tx has been locked in TxnBegin, so there is no need to lock it again
tx.UnsafePut(metaBucketName, consistentIndexKeyName, bs)
+ atomic.StoreUint64(&s.consistentIndex, ci)
}
func (s *store) ConsistentIndex() uint64 {
- // TODO: cache index in a uint64 field?
+ if ci := atomic.LoadUint64(&s.consistentIndex); ci > 0 {
+ return ci
+ }
tx := s.b.BatchTx()
tx.Lock()
defer tx.Unlock()
@@ -395,7 +405,9 @@ func (s *store) ConsistentIndex() uint64 {
if len(vs) == 0 {
return 0
}
- return binary.BigEndian.Uint64(vs[0])
+ v := binary.BigEndian.Uint64(vs[0])
+ atomic.StoreUint64(&s.consistentIndex, v)
+ return v
}
// appendMarkTombstone appends tombstone mark to normal revision bytes.
