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[1.3] Ensure the stats is always 64bit aligned #586

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Oct 25, 2023
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[1.3] Ensure the stats is always 64bit aligned #586

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15 changes: 12 additions & 3 deletions db.go
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,12 @@ const (
// 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.
type DB struct {
// Put `stats` at the first field to ensure it's 64-bit aligned. Note that
// the first word in an allocated struct can be relied upon to be 64-bit
// aligned. Refer to https://pkg.go.dev/sync/atomic#pkg-note-BUG. Also
// refer to discussion in https://github.com/etcd-io/bbolt/issues/577.
stats Stats

// When enabled, the database will perform a Check() after every commit.
// A panic is issued if the database is in an inconsistent state. This
// flag has a large performance impact so it should only be used for
Expand Down Expand Up @@ -147,7 +153,6 @@ type DB struct {
opened bool
rwtx *Tx
txs []*Tx
stats Stats

freelist *freelist
freelistLoad sync.Once
Expand Down Expand Up @@ -1282,6 +1287,12 @@ var DefaultOptions = &Options{

// Stats represents statistics about the database.
type Stats struct {
// Put `TxStats` at the first field to ensure it's 64-bit aligned. Note
// that the first word in an allocated struct can be relied upon to be
// 64-bit aligned. Refer to https://pkg.go.dev/sync/atomic#pkg-note-BUG.
// Also refer to discussion in https://github.com/etcd-io/bbolt/issues/577.
TxStats TxStats // global, ongoing stats.

// Freelist stats
FreePageN int // total number of free pages on the freelist
PendingPageN int // total number of pending pages on the freelist
Expand All @@ -1291,8 +1302,6 @@ type Stats struct {
// Transaction stats
TxN int // total number of started read transactions
OpenTxN int // number of currently open read transactions

TxStats TxStats // global, ongoing stats.
}

// Sub calculates and returns the difference between two sets of database stats.
Expand Down