sql: pool flow allocations

Previously, new structs for rowBasedFlow and vectorizedFlow would be
allocated upon creation. This commit creates pools for both of them.
flowinfra.Releasable interface is moved into execinfra package because
now components from rowflow, rowexec, and colflow packages implement
that.

In order to actually be able to release the flow structs, I needed to
create separate Cleanup methods (which still share most of the logic)
which allows for removal of vectorized memory monitoring logic from
the shared FlowCtx.

Release note: None

pkg/sql/colflow/vectorized_flow.go

@@ -39,13 +39,32 @@ type vectorizedFlow struct {
 	*flowinfra.FlowBase
 	// operatorConcurrency is set if any operators are executed in parallel.
 	operatorConcurrency bool
+
+	// streamingMemAccount is the memory account that is tracking the static
+	// memory usage of the whole vectorized flow as well as all dynamic memory of
+	// the streaming components.
+	streamingMemAccount *mon.BoundAccount
+
+	// bufferingMemMonitors are the memory monitors of the buffering components.
+	bufferingMemMonitors []*mon.BytesMonitor
+	// bufferingMemAccounts are the memory accounts that are tracking the dynamic
+	// memory usage of the buffering components.
+	bufferingMemAccounts []*mon.BoundAccount
 }
 
 var _ flowinfra.Flow = &vectorizedFlow{}
 
+var vectorizedFlowPool = sync.Pool{
+	New: func() interface{} {
+		return &vectorizedFlow{}
+	},
+}
+
 // NewVectorizedFlow creates a new vectorized flow given the flow base.
 func NewVectorizedFlow(base *flowinfra.FlowBase) flowinfra.Flow {
-	return &vectorizedFlow{FlowBase: base}
+	vf := vectorizedFlowPool.Get().(*vectorizedFlow)
+	vf.FlowBase = base
+	return vf
 }
 
 // Setup is part of the flowinfra.Flow interface.
@@ -55,7 +74,7 @@ func (f *vectorizedFlow) Setup(
 	f.SetSpec(spec)
 	log.VEventf(ctx, 1, "setting up vectorize flow %s", f.ID.Short())
 	streamingMemAccount := f.EvalCtx.Mon.MakeBoundAccount()
-	f.VectorizedStreamingMemAccount = &streamingMemAccount
+	f.streamingMemAccount = &streamingMemAccount
 	recordingStats := false
 	if sp := opentracing.SpanFromContext(ctx); sp != nil && tracing.IsRecording(sp) {
 		recordingStats = true
@@ -73,11 +92,21 @@ func (f *vectorizedFlow) Setup(
 	_, err := creator.setupFlow(ctx, f.GetFlowCtx(), spec.Processors, &streamingMemAccount, opt)
 	if err == nil {
 		f.operatorConcurrency = creator.operatorConcurrency
-		f.VectorizedBufferingMemMonitors = append(f.VectorizedBufferingMemMonitors, creator.bufferingMemMonitors...)
-		f.VectorizedBufferingMemAccounts = append(f.VectorizedBufferingMemAccounts, creator.bufferingMemAccounts...)
+		f.bufferingMemMonitors = append(f.bufferingMemMonitors, creator.bufferingMemMonitors...)
+		f.bufferingMemAccounts = append(f.bufferingMemAccounts, creator.bufferingMemAccounts...)
 		log.VEventf(ctx, 1, "vectorized flow setup succeeded")
 		return nil
 	}
+	f.streamingMemAccount.Close(ctx)
+	// It is (theoretically) possible that some of the memory monitoring
+	// infrastructure was created even in case of an error, and we need to clean
+	// that up.
+	for _, memAcc := range creator.bufferingMemAccounts {
+		memAcc.Close(ctx)
+	}
+	for _, memMonitor := range creator.bufferingMemMonitors {
+		memMonitor.Stop(ctx)
+	}
 	log.VEventf(ctx, 1, "failed to vectorize: %s", err)
 	return err
 }
@@ -87,6 +116,26 @@ func (f *vectorizedFlow) ConcurrentExecution() bool {
 	return f.operatorConcurrency || f.FlowBase.ConcurrentExecution()
 }
 
+// Release releases this vectorizedFlow back to the pool.
+func (f *vectorizedFlow) Release() {
+	*f = vectorizedFlow{}
+	vectorizedFlowPool.Put(f)
+}
+
+// Cleanup is part of the Flow interface.
+func (f *vectorizedFlow) Cleanup(ctx context.Context) {
+	// This cleans up all the memory monitoring of the vectorized flow.
+	f.streamingMemAccount.Close(ctx)
+	for _, memAcc := range f.bufferingMemAccounts {
+		memAcc.Close(ctx)
+	}
+	for _, memMonitor := range f.bufferingMemMonitors {
+		memMonitor.Stop(ctx)
+	}
+	f.FlowBase.Cleanup(ctx)
+	f.Release()
+}
+
 // wrapWithVectorizedStatsCollector creates a new exec.VectorizedStatsCollector
 // that wraps op and connects the newly created wrapper with those
 // corresponding to operators in inputs (the latter must have already been

pkg/sql/execinfra/base.go

@@ -188,6 +188,14 @@ func Run(ctx context.Context, src RowSource, dst RowReceiver) {
 	}
 }
 
+// Releasable is an interface for objects than can be Released back into a
+// memory pool when finished.
+type Releasable interface {
+	// Release allows this object to be returned to a memory pool. Objects must
+	// not be used after Release is called.
+	Release()
+}
+
 // DrainAndForwardMetadata calls src.ConsumerDone() (thus asking src for
 // draining metadata) and then forwards all the metadata to dst.
 //

pkg/sql/execinfra/flow_context.go

@@ -18,7 +18,6 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/execinfrapb"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
-	"github.com/cockroachdb/cockroach/pkg/util/mon"
 	"github.com/cockroachdb/cockroach/pkg/util/stop"
 )
 
@@ -60,18 +59,6 @@ type FlowCtx struct {
 
 	// Local is true if this flow is being run as part of a local-only query.
 	Local bool
-
-	// VectorizedStreamingMemAccount is the memory account that is tracking the
-	// static memory usage of the whole vectorized flow as well as all dynamic
-	// memory of the streaming vectorized components.
-	VectorizedStreamingMemAccount *mon.BoundAccount
-
-	// VectorizedBufferingMemMonitors are the memory monitors of the buffering
-	// vectorized components.
-	VectorizedBufferingMemMonitors []*mon.BytesMonitor
-	// VectorizedBufferingMemAccounts are the memory accounts that are tracking
-	// the dynamic memory usage of the buffering vectorized components.
-	VectorizedBufferingMemAccounts []*mon.BoundAccount
 }
 
 // NewEvalCtx returns a modifiable copy of the FlowCtx's EvalContext.

pkg/sql/flowinfra/flow.go

@@ -419,22 +419,13 @@ type Releasable interface {
 }
 
 // Cleanup is part of the Flow interface.
+// NOTE: this implements only the shared clean up logic between row-based and
+// vectorized flows.
 func (f *FlowBase) Cleanup(ctx context.Context) {
 	if f.status == FlowFinished {
 		panic("flow cleanup called twice")
 	}
 
-	// This cleans up all the memory monitoring of the vectorized flow.
-	if f.VectorizedStreamingMemAccount != nil {
-		f.VectorizedStreamingMemAccount.Close(ctx)
-	}
-	for _, memAcc := range f.VectorizedBufferingMemAccounts {
-		memAcc.Close(ctx)
-	}
-	for _, memMon := range f.VectorizedBufferingMemMonitors {
-		memMon.Stop(ctx)
-	}
-
 	// This closes the monitor opened in ServerImpl.setupFlow.
 	f.EvalCtx.Stop(ctx)
 	for _, p := range f.processors {
@@ -453,7 +444,6 @@ func (f *FlowBase) Cleanup(ctx context.Context) {
 	f.status = FlowFinished
 	f.ctxCancel()
 	f.doneFn()
-	f.doneFn = nil
 	sp.Finish()
 }
 

pkg/sql/rowexec/tablereader.go

@@ -59,6 +59,7 @@ type tableReader struct {
 var _ execinfra.Processor = &tableReader{}
 var _ execinfra.RowSource = &tableReader{}
 var _ execinfrapb.MetadataSource = &tableReader{}
+var _ execinfra.Releasable = &tableReader{}
 
 const tableReaderProcName = "table reader"
 

pkg/sql/rowflow/row_based_flow.go

@@ -13,6 +13,7 @@ package rowflow
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"github.com/cockroachdb/cockroach/pkg/sql/execinfra"
 	"github.com/cockroachdb/cockroach/pkg/sql/execinfrapb"
@@ -31,9 +32,17 @@ type rowBasedFlow struct {
 
 var _ flowinfra.Flow = &rowBasedFlow{}
 
+var rowBasedFlowPool = sync.Pool{
+	New: func() interface{} {
+		return &rowBasedFlow{}
+	},
+}
+
 // NewRowBasedFlow returns a row based flow using base as its FlowBase.
 func NewRowBasedFlow(base *flowinfra.FlowBase) flowinfra.Flow {
-	return &rowBasedFlow{FlowBase: base}
+	rbf := rowBasedFlowPool.Get().(*rowBasedFlow)
+	rbf.FlowBase = base
+	return rbf
 }
 
 // Setup if part of the flowinfra.Flow interface.
@@ -385,6 +394,18 @@ func (f *rowBasedFlow) setupRouter(spec *execinfrapb.OutputRouterSpec) (router,
 	return makeRouter(spec, streams)
 }
 
+// Release releases this rowBasedFlow back to the pool.
+func (f *rowBasedFlow) Release() {
+	*f = rowBasedFlow{}
+	rowBasedFlowPool.Put(f)
+}
+
+// Cleanup is part of the Flow interface.
+func (f *rowBasedFlow) Cleanup(ctx context.Context) {
+	f.FlowBase.Cleanup(ctx)
+	f.Release()
+}
+
 type copyingRowReceiver struct {
 	execinfra.RowReceiver
 	alloc sqlbase.EncDatumRowAlloc