*: remove goroutine pool (#7564)

goroutine pool was introduced to handle stack copy cost, Go1.11 has 
many optimizations for stack copy, after upgrading to Go1.1, goroutine
pool is not necessary any more.

distsql/select_result.go

@@ -25,7 +25,6 @@ import (
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/chunk"
 	"github.com/pingcap/tidb/util/codec"
-	"github.com/pingcap/tidb/util/goroutine_pool"
 	"github.com/pingcap/tipb/go-tipb"
 	"golang.org/x/net/context"
 )
@@ -35,10 +34,6 @@ var (
 	_ SelectResult = (*streamResult)(nil)
 )
 
-var (
-	selectResultGP = gp.New(time.Minute * 2)
-)
-
 // SelectResult is an iterator of coprocessor partial results.
 type SelectResult interface {
 	// Fetch fetches partial results from client.
@@ -75,9 +70,7 @@ type selectResult struct {
 }
 
 func (r *selectResult) Fetch(ctx context.Context) {
-	selectResultGP.Go(func() {
-		r.fetch(ctx)
-	})
+	go r.fetch(ctx)
 }
 
 func (r *selectResult) fetch(ctx context.Context) {

store/tikv/2pc.go

@@ -28,7 +28,6 @@ import (
 	"github.com/pingcap/tidb/store/tikv/tikvrpc"
 	"github.com/pingcap/tidb/tablecodec"
 	"github.com/pingcap/tidb/terror"
-	"github.com/pingcap/tidb/util/goroutine_pool"
 	binlog "github.com/pingcap/tipb/go-binlog"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
@@ -42,8 +41,6 @@ const (
 	actionCleanup  twoPhaseCommitAction = 3
 )
 
-var twoPhaseCommitGP = gp.New(3 * time.Minute)
-
 func (ca twoPhaseCommitAction) String() string {
 	switch ca {
 	case actionPrewrite:
@@ -225,13 +222,13 @@ func (c *twoPhaseCommitter) doActionOnKeys(bo *Backoffer, action twoPhaseCommitA
 	}
 	if action == actionCommit {
 		// Commit secondary batches in background goroutine to reduce latency.
-		twoPhaseCommitGP.Go(func() {
+		go func() {
 			e := c.doActionOnBatches(bo, action, batches)
 			if e != nil {
 				log.Debugf("con:%d 2PC async doActionOnBatches %s err: %v", c.connID, action, e)
 				metrics.TiKVSecondaryLockCleanupFailureCounter.WithLabelValues("commit").Inc()
 			}
-		})
+		}()
 	} else {
 		err = c.doActionOnBatches(bo, action, batches)
 	}
@@ -272,7 +269,7 @@ func (c *twoPhaseCommitter) doActionOnBatches(bo *Backoffer, action twoPhaseComm
 	for _, batch1 := range batches {
 
 		batch := batch1
-		twoPhaseCommitGP.Go(func() {
+		go func() {
 			if action == actionCommit {
 				// Because the secondary batches of the commit actions are implemented to be
 				// committed asynchronously in background goroutines, we should not
@@ -288,7 +285,7 @@ func (c *twoPhaseCommitter) doActionOnBatches(bo *Backoffer, action twoPhaseComm
 				defer singleBatchCancel()
 				ch <- singleBatchActionFunc(singleBatchBackoffer, batch)
 			}
-		})
+		}()
 	}
 	var err error
 	for i := 0; i < len(batches); i++ {
@@ -571,7 +568,7 @@ func (c *twoPhaseCommitter) execute(ctx context.Context) error {
 		c.mu.RUnlock()
 		if !committed && !undetermined {
 			c.cleanWg.Add(1)
-			twoPhaseCommitGP.Go(func() {
+			go func() {
 				err := c.cleanupKeys(NewBackoffer(context.Background(), cleanupMaxBackoff).WithVars(c.txn.vars), c.keys)
 				if err != nil {
 					metrics.TiKVSecondaryLockCleanupFailureCounter.WithLabelValues("rollback").Inc()
@@ -580,7 +577,7 @@ func (c *twoPhaseCommitter) execute(ctx context.Context) error {
 					log.Infof("con:%d 2PC clean up done, tid: %d", c.connID, c.startTS)
 				}
 				c.cleanWg.Done()
-			})
+			}()
 		}
 	}()
 

store/tikv/coprocessor.go

@@ -31,14 +31,11 @@ import (
 	"github.com/pingcap/tidb/metrics"
 	"github.com/pingcap/tidb/store/tikv/tikvrpc"
 	"github.com/pingcap/tidb/util/execdetails"
-	"github.com/pingcap/tidb/util/goroutine_pool"
 	"github.com/pingcap/tipb/go-tipb"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
 )
 
-var copIteratorGP = gp.New(time.Minute)
-
 // CopClient is coprocessor client.
 type CopClient struct {
 	store *tikvStore
@@ -452,9 +449,7 @@ func (it *copIterator) open(ctx context.Context) {
 			finishCh: it.finishCh,
 			vars:     it.vars,
 		}
-		copIteratorGP.Go(func() {
-			worker.run(ctx)
-		})
+		go worker.run(ctx)
 	}
 	taskSender := &copIteratorTaskSender{
 		taskCh:   taskCh,
@@ -463,7 +458,7 @@ func (it *copIterator) open(ctx context.Context) {
 		finishCh: it.finishCh,
 	}
 	taskSender.respChan = it.respChan
-	copIteratorGP.Go(taskSender.run)
+	go taskSender.run()
 }
 
 func (sender *copIteratorTaskSender) run() {

store/tikv/rawkv.go

@@ -23,12 +23,10 @@ import (
 	"github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/metrics"
 	"github.com/pingcap/tidb/store/tikv/tikvrpc"
-	"github.com/pingcap/tidb/util/goroutine_pool"
 	"golang.org/x/net/context"
 )
 
 var (
-	rawKVClientGP = gp.New(3 * time.Minute)
 	// MaxRawKVScanLimit is the maximum scan limit for rawkv Scan.
 	MaxRawKVScanLimit = 10240
 	// ErrMaxScanLimitExceeded is returned when the limit for rawkv Scan is to large.
@@ -349,11 +347,11 @@ func (c *RawKVClient) sendBatchReq(bo *Backoffer, keys [][]byte, cmdType tikvrpc
 	ches := make(chan singleBatchResp, len(batches))
 	for _, batch := range batches {
 		batch1 := batch
-		rawKVClientGP.Go(func() {
+		go func() {
 			singleBatchBackoffer, singleBatchCancel := bo.Fork()
 			defer singleBatchCancel()
 			ches <- c.doBatchReq(singleBatchBackoffer, batch1, cmdType)
-		})
+		}()
 	}
 
 	var firstError error
@@ -507,11 +505,11 @@ func (c *RawKVClient) sendBatchPut(bo *Backoffer, keys, values [][]byte) error {
 	ch := make(chan error, len(batches))
 	for _, batch := range batches {
 		batch1 := batch
-		rawKVClientGP.Go(func() {
+		go func() {
 			singleBatchBackoffer, singleBatchCancel := bo.Fork()
 			defer singleBatchCancel()
 			ch <- c.doBatchPut(singleBatchBackoffer, batch1)
-		})
+		}()
 	}
 
 	for i := 0; i < len(batches); i++ {

store/tikv/snapshot.go

@@ -26,7 +26,6 @@ import (
 	"github.com/pingcap/tidb/metrics"
 	"github.com/pingcap/tidb/store/tikv/tikvrpc"
 	"github.com/pingcap/tidb/tablecodec"
-	"github.com/pingcap/tidb/util/goroutine_pool"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
 )
@@ -51,8 +50,6 @@ type tikvSnapshot struct {
 	vars         *kv.Variables
 }
 
-var snapshotGP = gp.New(time.Minute)
-
 // newTiKVSnapshot creates a snapshot of an TiKV store.
 func newTiKVSnapshot(store *tikvStore, ver kv.Version) *tikvSnapshot {
 	return &tikvSnapshot{
@@ -123,11 +120,11 @@ func (s *tikvSnapshot) batchGetKeysByRegions(bo *Backoffer, keys [][]byte, colle
 	ch := make(chan error)
 	for _, batch1 := range batches {
 		batch := batch1
-		snapshotGP.Go(func() {
+		go func() {
 			backoffer, cancel := bo.Fork()
 			defer cancel()
 			ch <- s.batchGetSingleRegion(backoffer, batch, collectF)
-		})
+		}()
 	}
 	for i := 0; i < len(batches); i++ {
 		if e := <-ch; e != nil {