stream: group bool fields at tail of clientStream to reduce allocator size class 288B→256B (#9281)
diff --git a/stream.go b/stream.go
index d3e2727..e01b9e0 100644
--- a/stream.go
+++ b/stream.go
@@ -689,10 +689,6 @@
cancel context.CancelFunc // cancels all attempts
- sentLast bool // sent an end stream
-
- receivedFirstMsg bool // set after the first message is received
-
methodConfig *MethodConfig
ctx context.Context // the application's context, wrapped by stats/tracing
@@ -700,19 +696,10 @@
retryThrottler *retryThrottler // The throttler active when the RPC began.
binlogs []binarylog.MethodLogger
- // serverHeaderBinlogged is a boolean for whether server header has been
- // logged. Server header will be logged when the first time one of those
- // happens: stream.Header(), stream.Recv().
- //
- // It's only read and used by Recv() and Header(), so it doesn't need to be
- // synchronized.
- serverHeaderBinlogged bool
mu sync.Mutex
- firstAttempt bool // if true, transparent retry is valid
- numRetries int // exclusive of transparent retry attempt(s)
- numRetriesSincePushback int // retries since pushback; to reset backoff
- finished bool // TODO: replace with atomic cmpxchg or sync.Once?
+ numRetries int // exclusive of transparent retry attempt(s)
+ numRetriesSincePushback int // retries since pushback; to reset backoff
// attempt is the active client stream attempt.
// The only place where it is written is the newAttemptLocked method and this method never writes nil.
// So, attempt can be nil only inside newClientStream function when clientStream is first created.
@@ -722,13 +709,33 @@
// place where we need to check if the attempt is nil.
attempt *csAttempt
// TODO(hedging): hedging will have multiple attempts simultaneously.
- committed bool // active attempt committed for retry?
onCommit func()
replayBuffer []replayOp // operations to replay on retry
replayBufferSize int // current size of replayBuffer
+
+ // Bool fields are grouped at the tail to eliminate the alignment padding
+ // that would otherwise follow each bool when the next field is pointer- or
+ // int-sized. See https://github.com/grpc/grpc-go/issues/9280 for benchmarks.
+ // Add new bool fields here, not inline above.
+
+ // Not guarded by mu.
+ sentLast bool // sent an end stream
+ receivedFirstMsg bool // set after the first message is received
+ // serverHeaderBinlogged is a boolean for whether server header has been
+ // logged. Server header will be logged when the first time one of those
+ // happens: stream.Header(), stream.Recv().
+ //
+ // It's only read and used by Recv() and Header(), so it doesn't need to be
+ // synchronized.
+ serverHeaderBinlogged bool
// nameResolutionDelay indicates if there was a delay in the name resolution.
// This field is only valid on client side, it's always false on server side.
nameResolutionDelay bool
+
+ // Guarded by mu.
+ firstAttempt bool // if true, transparent retry is valid
+ finished bool // TODO: replace with atomic cmpxchg or sync.Once?
+ committed bool // active attempt committed for retry?
}
type replayOp struct {
