Merge branch 'LK4D4-pool_allocate'

2 files changed, 36 insertions, 3 deletions

diff --git a/db.go b/db.go
index 8503665..9048f6c 100644
--- a/db.go
+++ b/db.go
@@ -36,6 +36,9 @@ const (
 	DefaultAllocSize         = 16 * 1024 * 1024
 )
 
+// default page size for db is set to the OS page size.
+var defaultPageSize = os.Getpagesize()
+
 // DB represents a collection of buckets persisted to a file on disk.
 // All data access is performed through transactions which can be obtained through the DB.
 // All the functions on DB will return a ErrDatabaseNotOpen if accessed before Open() is called.
@@ -107,6 +110,8 @@ type DB struct {
 	freelist *freelist
 	stats    Stats
 
+	pagePool sync.Pool
+
 	batchMu sync.Mutex
 	batch   *batch
 
@@ -206,6 +211,13 @@ func Open(path string, mode os.FileMode, options *Options) (*DB, error) {
 		}
 	}
 
+	// Initialize page pool.
+	db.pagePool = sync.Pool{
+		New: func() interface{} {
+			return make([]byte, db.pageSize)
+		},
+	}
+
 	// Memory map the data file.
 	if err := db.mmap(options.InitialMmapSize); err != nil {
 		_ = db.close()
@@ -787,7 +799,12 @@ func (db *DB) meta() *meta {
 // allocate returns a contiguous block of memory starting at a given page.
 func (db *DB) allocate(count int) (*page, error) {
 	// Allocate a temporary buffer for the page.
-	buf := make([]byte, count*db.pageSize)
+	var buf []byte
+	if count == 1 {
+		buf = db.pagePool.Get().([]byte)
+	} else {
+		buf = make([]byte, count*db.pageSize)
+	}
 	p := (*page)(unsafe.Pointer(&buf[0]))
 	p.overflow = uint32(count - 1)
 
diff --git a/tx.go b/tx.go
index b8510fd..1cfb4cd 100644
--- a/tx.go
+++ b/tx.go
@@ -473,6 +473,8 @@ func (tx *Tx) write() error {
 	for _, p := range tx.pages {
 		pages = append(pages, p)
 	}
+	// Clear out page cache early.
+	tx.pages = make(map[pgid]*page)
 	sort.Sort(pages)
 
 	// Write pages to disk in order.
@@ -517,8 +519,22 @@ func (tx *Tx) write() error {
 		}
 	}
 
-	// Clear out page cache.
-	tx.pages = make(map[pgid]*page)
+	// Put small pages back to page pool.
+	for _, p := range pages {
+		// Ignore page sizes over 1 page.
+		// These are allocated using make() instead of the page pool.
+		if int(p.overflow) != 0 {
+			continue
+		}
+
+		buf := (*[maxAllocSize]byte)(unsafe.Pointer(p))[:tx.db.pageSize]
+
+		// See https://go.googlesource.com/go/+/f03c9202c43e0abb130669852082117ca50aa9b1
+		for i := range buf {
+			buf[i] = 0
+		}
+		tx.db.pagePool.Put(buf)
+	}
 
 	return nil
 }