diff --git a/Makefile b/Makefile
index 47c0ef76f..0362f95b4 100644
--- a/Makefile
+++ b/Makefile
@@ -75,6 +75,8 @@ mlr:
 	go build github.com/johnkerl/miller/cmd/mlr
 mprof:
 	go build github.com/johnkerl/miller/cmd/mprof
+mprof2:
+	go build github.com/johnkerl/miller/cmd/mprof2
 
 # Please see comments in ./create-release-tarball as well as
 # https://miller.readthedocs.io/en/latest/build/#creating-a-new-release-for-developers
@@ -82,4 +84,4 @@ release_tarball: build check
 	./create-release-tarball
 
 # Go does its own dependency management, outside of make.
-.PHONY: build mlr mprof check unit_test regression_test fmt dev
+.PHONY: build mlr mprof mprof2 check unit_test regression_test fmt dev
diff --git a/cmd/mprof/main.go b/cmd/mprof/main.go
new file mode 100644
index 000000000..1bd60daab
--- /dev/null
+++ b/cmd/mprof/main.go
@@ -0,0 +1,679 @@
+// Experiments in performance/profiling.
+package main
+
+import (
+	"bufio"
+	"container/list"
+	"fmt"
+	"io"
+	"os"
+	"runtime"
+	"runtime/debug"
+	"runtime/pprof"
+	"strconv"
+	"strings"
+	//"time"
+
+	"github.com/pkg/profile" // for trace.out
+
+	"github.com/johnkerl/miller/internal/pkg/cli"
+	"github.com/johnkerl/miller/internal/pkg/input"
+	"github.com/johnkerl/miller/internal/pkg/lib"
+	"github.com/johnkerl/miller/internal/pkg/types"
+)
+
+func main() {
+
+	// Respect env $GOMAXPROCS, if provided, else set default.
+	haveSetGoMaxProcs := false
+	goMaxProcsString := os.Getenv("GOMAXPROCS")
+	if goMaxProcsString != "" {
+		goMaxProcs, err := strconv.Atoi(goMaxProcsString)
+		if err != nil {
+			runtime.GOMAXPROCS(goMaxProcs)
+			haveSetGoMaxProcs = true
+		}
+	}
+	if !haveSetGoMaxProcs {
+		// As of Go 1.16 this is the default anyway. For 1.15 and below we need
+		// to explicitly set this.
+		runtime.GOMAXPROCS(runtime.NumCPU())
+	}
+
+	debug.SetGCPercent(500) // Empirical: See README-profiling.md
+
+	if os.Getenv("MPROF_PPROF") != "" {
+		// profiling with cpu.pprof and go tool pprof -http=:8080 cpu.pprof
+		profFilename := "cpu.pprof"
+		handle, err := os.Create(profFilename)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, os.Args[0], ": ", "Could not start CPU profile: ", err)
+			return
+		}
+		defer handle.Close()
+
+		if err := pprof.StartCPUProfile(handle); err != nil {
+			fmt.Fprintln(os.Stderr, os.Args[0], ": ", "Could not start CPU profile: ", err)
+			return
+		}
+		defer pprof.StopCPUProfile()
+
+		fmt.Fprintf(os.Stderr, "CPU profile started.\n")
+		fmt.Fprintf(os.Stderr, "go tool pprof -http=:8080 cpu.pprof\n")
+		defer fmt.Fprintf(os.Stderr, "CPU profile finished.\n")
+	}
+
+	if os.Getenv("MPROF_TRACE") != "" {
+		// tracing with trace.out and go tool trace trace.out
+		fmt.Fprintf(os.Stderr, "go tool trace trace.out\n")
+		defer profile.Start(profile.TraceProfile, profile.ProfilePath(".")).Stop()
+	}
+
+	options := cli.DefaultOptions()
+	if os.Getenv("MPROF_JIT") != "" {
+		fmt.Fprintf(os.Stderr, "JIT ON\n")
+		types.SetInferrerStringOnly()
+	} else {
+		fmt.Fprintf(os.Stderr, "JIT OFF\n")
+	}
+
+	filenames := os.Args[1:]
+	lib.InternalCodingErrorIf(len(filenames) != 1)
+	filename := filenames[0]
+
+	err := Stream(filename, options, os.Stdout)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "mlr: %v.\n", err)
+		os.Exit(1)
+	}
+}
+
+func getBatchSize() int {
+	m := 1
+	sm := os.Getenv("MPROF_BATCH")
+	if sm != "" {
+		im, err := strconv.ParseInt(sm, 0, 64)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		m = int(im)
+	}
+	fmt.Fprintf(os.Stderr, "IBATCH %d\n", m)
+	return m
+}
+
+// ================================================================
+type IRecordReader interface {
+	Read(ioChannel chan<- *list.List) error
+}
+
+func Stream(
+	filename string,
+	options *cli.TOptions,
+	outputStream io.WriteCloser,
+) error {
+	initialContext := types.NewContext()
+
+	// Instantiate the record-reader
+	var recordReader IRecordReader
+	var err error
+	if os.Getenv("MPROF_PIPE") != "" {
+		fmt.Fprintf(os.Stderr, "PIPELINE ON\n")
+		recordReader, err = NewRecordReaderDKVPListPipelined(&options.ReaderOptions, filename, initialContext)
+	} else if os.Getenv("MPROF_CHAN") != "" {
+		fmt.Fprintf(os.Stderr, "CHAN ON\n")
+		recordReader, err = NewRecordReaderDKVPChanPipelined(&options.ReaderOptions, filename, initialContext)
+	} else {
+		fmt.Fprintf(os.Stderr, "PIPELINE OFF\n")
+		recordReader, err = NewRecordReaderDKVPNonPipelined(&options.ReaderOptions, filename, initialContext)
+	}
+	if err != nil {
+		return err
+	}
+
+	// Instantiate the record-writer
+	recordWriter, err := NewRecordWriterDKVP2(&options.WriterOptions)
+	if err != nil {
+		return err
+	}
+
+	ostream := bufio.NewWriter(os.Stdout)
+	defer ostream.Flush()
+
+	ioChannel := make(chan *list.List, 1)
+	errorChannel := make(chan error, 1)
+	doneWritingChannel := make(chan bool, 1)
+
+	go recordReader.Read(ioChannel)
+	go ChannelWriter(ioChannel, recordWriter, doneWritingChannel, ostream)
+
+	done := false
+	for !done {
+		select {
+		case err := <-errorChannel:
+			////fmt.Fprintf(os.Stderr, "ECHAN READ\n")
+			fmt.Fprintln(os.Stderr, "mlr", ": ", err)
+			os.Exit(1)
+		case _ = <-doneWritingChannel:
+			////fmt.Fprintf(os.Stderr, "ZCHAN READ\n")
+			done = true
+			break
+		}
+	}
+
+	return nil
+}
+
+// ================================================================
+
+type RecordReaderDKVPNonPipelined struct {
+	readerOptions  *cli.TReaderOptions
+	filename       string
+	initialContext *types.Context
+}
+
+func NewRecordReaderDKVPNonPipelined(
+	readerOptions *cli.TReaderOptions,
+	filename string,
+	initialContext *types.Context,
+) (*RecordReaderDKVPNonPipelined, error) {
+	return &RecordReaderDKVPNonPipelined{
+		readerOptions:  readerOptions,
+		filename:       filename,
+		initialContext: initialContext,
+	}, nil
+}
+
+func (reader *RecordReaderDKVPNonPipelined) Read(
+	inputChannel chan<- *list.List,
+) error {
+	handle, err := lib.OpenFileForRead(
+		reader.filename,
+		reader.readerOptions.Prepipe,
+		reader.readerOptions.PrepipeIsRaw,
+		reader.readerOptions.FileInputEncoding,
+	)
+	if err != nil {
+		return err
+	} else {
+		reader.processHandle(handle, reader.filename, reader.initialContext, inputChannel)
+		handle.Close()
+	}
+
+	return nil
+}
+
+// ----------------------------------------------------------------
+
+func (reader *RecordReaderDKVPNonPipelined) processHandle(
+	handle io.Reader,
+	filename string,
+	context *types.Context,
+	inputChannel chan<- *list.List,
+) {
+	context.UpdateForStartOfFile(filename)
+	scanner := input.NewLineScanner(handle, reader.readerOptions.IRS)
+
+	recordsAndContexts := list.New()
+
+	m := getBatchSize()
+	i := 0
+	for scanner.Scan() {
+		i += 1
+
+		line := scanner.Text()
+
+		record := reader.recordFromDKVPLine(line)
+		context.UpdateForInputRecord()
+		recordAndContext := types.NewRecordAndContext(record, context)
+		recordsAndContexts.PushBack(recordAndContext)
+
+		if i%m == 0 {
+			inputChannel <- recordsAndContexts
+			recordsAndContexts = list.New()
+		}
+
+	}
+	if recordsAndContexts.Len() > 0 {
+		inputChannel <- recordsAndContexts
+	}
+	inputChannel <- nil // end-of-stream marker
+}
+
+func (reader *RecordReaderDKVPNonPipelined) recordFromDKVPLine(
+	line string,
+) *types.Mlrmap {
+	record := types.NewMlrmap()
+
+	var pairs []string
+	if reader.readerOptions.IFSRegex == nil { // e.g. --no-ifs-regex
+		pairs = lib.SplitString(line, reader.readerOptions.IFS)
+	} else {
+		pairs = lib.RegexSplitString(reader.readerOptions.IFSRegex, line, -1)
+	}
+
+	for i, pair := range pairs {
+		var kv []string
+		if reader.readerOptions.IPSRegex == nil { // e.g. --no-ips-regex
+			kv = strings.SplitN(line, reader.readerOptions.IPS, 2)
+		} else {
+			kv = lib.RegexSplitString(reader.readerOptions.IPSRegex, pair, 2)
+		}
+
+		if len(kv) == 0 {
+			// Ignore. This is expected when splitting with repeated IFS.
+		} else if len(kv) == 1 {
+			// E.g the pair has no equals sign: "a" rather than "a=1" or
+			// "a=".  Here we use the positional index as the key. This way
+			// DKVP is a generalization of NIDX.
+			key := strconv.Itoa(i + 1) // Miller userspace indices are 1-up
+			value := types.MlrvalFromInferredTypeForDataFiles(kv[0])
+			record.PutReference(key, value)
+		} else {
+			key := kv[0]
+			value := types.MlrvalFromInferredTypeForDataFiles(kv[1])
+			record.PutReference(key, value)
+		}
+	}
+	return record
+}
+
+// ================================================================
+
+type RecordReaderDKVPListPipelined struct {
+	readerOptions  *cli.TReaderOptions
+	filename       string
+	initialContext *types.Context
+}
+
+func NewRecordReaderDKVPListPipelined(
+	readerOptions *cli.TReaderOptions,
+	filename string,
+	initialContext *types.Context,
+) (*RecordReaderDKVPListPipelined, error) {
+	return &RecordReaderDKVPListPipelined{
+		readerOptions:  readerOptions,
+		filename:       filename,
+		initialContext: initialContext,
+	}, nil
+}
+
+func (reader *RecordReaderDKVPListPipelined) Read(
+	inputChannel chan<- *list.List,
+) error {
+	handle, err := lib.OpenFileForRead(
+		reader.filename,
+		reader.readerOptions.Prepipe,
+		reader.readerOptions.PrepipeIsRaw,
+		reader.readerOptions.FileInputEncoding,
+	)
+	if err != nil {
+		return err
+	} else {
+		reader.processHandle(handle, reader.filename, reader.initialContext, inputChannel)
+		handle.Close()
+	}
+
+	eom := types.NewEndOfStreamMarker(reader.initialContext)
+	leom := list.New()
+	leom.PushBack(eom)
+	inputChannel <- leom
+	////fmt.Fprintf(os.Stderr, "IOCHAN WRITE EOM\n")
+	return nil
+}
+
+func lineProvider(
+	lineScanner *bufio.Scanner,
+	linesChannel chan<- *list.List,
+) {
+
+	lines := list.New()
+
+	m := getBatchSize()
+	i := 0
+	for lineScanner.Scan() {
+		i += 1
+		line := lineScanner.Text()
+		lines.PushBack(line)
+		if i%m == 0 {
+			linesChannel <- lines
+			lines = list.New()
+		}
+	}
+	if lines.Len() > 0 {
+		linesChannel <- lines
+	}
+	linesChannel <- nil // end-of-stream marker
+}
+
+func (reader *RecordReaderDKVPListPipelined) processHandle(
+	handle io.Reader,
+	filename string,
+	context *types.Context,
+	inputChannel chan<- *list.List,
+) {
+	context.UpdateForStartOfFile(filename)
+
+	lineScanner := input.NewLineScanner(handle, reader.readerOptions.IRS)
+	linesChannel := make(chan *list.List, 1)
+
+	go lineProvider(lineScanner, linesChannel)
+
+	for {
+		lines := <-linesChannel
+		if lines == nil {
+			break
+		}
+		recordsAndContexts := list.New()
+		for e := lines.Front(); e != nil; e = e.Next() {
+			line := e.Value.(string)
+			record := reader.recordFromDKVPLine(line)
+			context.UpdateForInputRecord()
+			recordAndContext := types.NewRecordAndContext(record, context)
+			recordsAndContexts.PushBack(recordAndContext)
+		}
+		inputChannel <- recordsAndContexts
+	}
+}
+
+func (reader *RecordReaderDKVPListPipelined) recordFromDKVPLine(
+	line string,
+) *types.Mlrmap {
+	record := types.NewMlrmap()
+
+	var pairs []string
+	if reader.readerOptions.IFSRegex == nil { // e.g. --no-ifs-regex
+		pairs = lib.SplitString(line, reader.readerOptions.IFS)
+	} else {
+		pairs = lib.RegexSplitString(reader.readerOptions.IFSRegex, line, -1)
+	}
+
+	for i, pair := range pairs {
+		var kv []string
+		if reader.readerOptions.IPSRegex == nil { // e.g. --no-ips-regex
+			kv = strings.SplitN(line, reader.readerOptions.IPS, 2)
+		} else {
+			kv = lib.RegexSplitString(reader.readerOptions.IPSRegex, pair, 2)
+		}
+
+		if len(kv) == 0 {
+			// Ignore. This is expected when splitting with repeated IFS.
+		} else if len(kv) == 1 {
+			// E.g the pair has no equals sign: "a" rather than "a=1" or
+			// "a=".  Here we use the positional index as the key. This way
+			// DKVP is a generalization of NIDX.
+			key := strconv.Itoa(i + 1) // Miller userspace indices are 1-up
+			value := types.MlrvalFromInferredTypeForDataFiles(kv[0])
+			record.PutReference(key, value)
+		} else {
+			key := kv[0]
+			value := types.MlrvalFromInferredTypeForDataFiles(kv[1])
+			record.PutReference(key, value)
+		}
+	}
+	return record
+}
+
+// ================================================================
+
+type RecordReaderDKVPChanPipelined struct {
+	readerOptions  *cli.TReaderOptions
+	filename       string
+	initialContext *types.Context
+}
+
+func NewRecordReaderDKVPChanPipelined(
+	readerOptions *cli.TReaderOptions,
+	filename string,
+	initialContext *types.Context,
+) (*RecordReaderDKVPChanPipelined, error) {
+	return &RecordReaderDKVPChanPipelined{
+		readerOptions:  readerOptions,
+		filename:       filename,
+		initialContext: initialContext,
+	}, nil
+}
+
+func (reader *RecordReaderDKVPChanPipelined) Read(
+	inputChannel chan<- *list.List,
+) error {
+	handle, err := lib.OpenFileForRead(
+		reader.filename,
+		reader.readerOptions.Prepipe,
+		reader.readerOptions.PrepipeIsRaw,
+		reader.readerOptions.FileInputEncoding,
+	)
+	if err != nil {
+		return err
+	} else {
+		reader.processHandle(handle, reader.filename, reader.initialContext, inputChannel)
+		handle.Close()
+	}
+
+	eom := types.NewEndOfStreamMarker(reader.initialContext)
+	leom := list.New()
+	leom.PushBack(eom)
+	inputChannel <- leom
+	////fmt.Fprintf(os.Stderr, "IOCHAN WRITE EOM\n")
+	return nil
+}
+
+func chanProvider(
+	lineScanner *bufio.Scanner,
+	linesChannel chan<- string,
+) {
+	for lineScanner.Scan() {
+		linesChannel <- lineScanner.Text()
+	}
+	close(linesChannel) // end-of-stream marker
+}
+
+// TODO: comment copiously we're trying to handle slow/fast/short/long
+// reads: tail -f, smallfile, bigfile.
+func (reader *RecordReaderDKVPChanPipelined) getRecordBatch(
+	linesChannel <-chan string,
+	maxBatchSize int,
+	context *types.Context,
+) (
+	recordsAndContexts *list.List,
+	eof bool,
+) {
+	//fmt.Printf("GRB ENTER\n")
+	recordsAndContexts = list.New()
+	eof = false
+
+	for i := 0; i < maxBatchSize; i++ {
+		//fmt.Fprintf(os.Stderr, "-- %d/%d %d/%d\n", i, maxBatchSize, len(linesChannel), cap(linesChannel))
+		if len(linesChannel) == 0 && i > 0 {
+			//fmt.Println(" .. BREAK")
+			break
+		}
+		//fmt.Println(" .. B:BLOCK")
+		line, more := <-linesChannel
+		//fmt.Printf(" .. E:BLOCK <<%s>> %v\n", line, more)
+		if !more {
+			eof = true
+			break
+		}
+
+		record := reader.recordFromDKVPLine(line)
+		context.UpdateForInputRecord()
+		recordAndContext := types.NewRecordAndContext(record, context)
+		recordsAndContexts.PushBack(recordAndContext)
+	}
+
+	//fmt.Printf("GRB EXIT\n")
+	return recordsAndContexts, eof
+}
+
+func (reader *RecordReaderDKVPChanPipelined) processHandle(
+	handle io.Reader,
+	filename string,
+	context *types.Context,
+	inputChannel chan<- *list.List,
+) {
+	context.UpdateForStartOfFile(filename)
+	m := getBatchSize()
+
+	lineScanner := input.NewLineScanner(handle, reader.readerOptions.IRS)
+	linesChannel := make(chan string, m)
+	go chanProvider(lineScanner, linesChannel)
+
+	eof := false
+	for !eof {
+		var recordsAndContexts *list.List
+		recordsAndContexts, eof = reader.getRecordBatch(linesChannel, m, context)
+		//fmt.Fprintf(os.Stderr, "GOT RECORD BATCH OF LENGTH %d\n", recordsAndContexts.Len())
+		inputChannel <- recordsAndContexts
+	}
+}
+
+func (reader *RecordReaderDKVPChanPipelined) recordFromDKVPLine(
+	line string,
+) *types.Mlrmap {
+	record := types.NewMlrmap()
+
+	var pairs []string
+	if reader.readerOptions.IFSRegex == nil { // e.g. --no-ifs-regex
+		pairs = lib.SplitString(line, reader.readerOptions.IFS)
+	} else {
+		pairs = lib.RegexSplitString(reader.readerOptions.IFSRegex, line, -1)
+	}
+
+	for i, pair := range pairs {
+		var kv []string
+		if reader.readerOptions.IPSRegex == nil { // e.g. --no-ips-regex
+			kv = strings.SplitN(line, reader.readerOptions.IPS, 2)
+		} else {
+			kv = lib.RegexSplitString(reader.readerOptions.IPSRegex, pair, 2)
+		}
+
+		if len(kv) == 0 {
+			// Ignore. This is expected when splitting with repeated IFS.
+		} else if len(kv) == 1 {
+			// E.g the pair has no equals sign: "a" rather than "a=1" or
+			// "a=".  Here we use the positional index as the key. This way
+			// DKVP is a generalization of NIDX.
+			key := strconv.Itoa(i + 1) // Miller userspace indices are 1-up
+			value := types.MlrvalFromInferredTypeForDataFiles(kv[0])
+			record.PutReference(key, value)
+		} else {
+			key := kv[0]
+			value := types.MlrvalFromInferredTypeForDataFiles(kv[1])
+			record.PutReference(key, value)
+		}
+	}
+	return record
+}
+
+// ================================================================
+func ChannelWriter(
+	outputChannel <-chan *list.List,
+	recordWriter *RecordWriterDKVP2,
+	doneChannel chan<- bool,
+	ostream *bufio.Writer,
+) {
+	for {
+		recordsAndContexts := <-outputChannel
+		if recordsAndContexts != nil {
+			//fmt.Fprintf(os.Stderr, "IOCHAN READ BATCH LEN %d\n", recordsAndContexts.Len())
+		}
+		if recordsAndContexts == nil {
+			//fmt.Fprintf(os.Stderr, "IOCHAN READ EOS\n")
+			doneChannel <- true
+			break
+		}
+
+		for e := recordsAndContexts.Front(); e != nil; e = e.Next() {
+			recordAndContext := e.Value.(*types.RecordAndContext)
+
+			// Three things can come through:
+			// * End-of-stream marker
+			// * Non-nil records to be printed
+			// * Strings to be printed from put/filter DSL print/dump/etc
+			//   statements. They are handled here rather than fmt.Println directly
+			//   in the put/filter handlers since we want all print statements and
+			//   record-output to be in the same goroutine, for deterministic
+			//   output ordering.
+			if !recordAndContext.EndOfStream {
+				record := recordAndContext.Record
+				if record != nil {
+					recordWriter.Write(record, ostream)
+				}
+
+				outputString := recordAndContext.OutputString
+				if outputString != "" {
+					fmt.Print(outputString)
+				}
+
+			} else {
+				// Let the record-writers drain their output, if they have any
+				// queued up. For example, PPRINT needs to see all same-schema
+				// records before printing any, since it needs to compute max width
+				// down columns.
+				recordWriter.Write(nil, ostream)
+				doneChannel <- true
+				////fmt.Fprintf(os.Stderr, "ZCHAN WRITE\n")
+				return
+			}
+		}
+	}
+}
+
+// ================================================================
+
+type RecordWriterDKVP2 struct {
+	writerOptions *cli.TWriterOptions
+	buffer        bool
+}
+
+func NewRecordWriterDKVP2(writerOptions *cli.TWriterOptions) (*RecordWriterDKVP2, error) {
+	buffer := false
+	if os.Getenv("MPROF_BUFFER") != "" {
+		fmt.Fprintf(os.Stderr, "BUFFER ON\n")
+		buffer = true
+	} else {
+		fmt.Fprintf(os.Stderr, "BUFFER OFF\n")
+	}
+	return &RecordWriterDKVP2{
+		writerOptions: writerOptions,
+		buffer:        buffer,
+	}, nil
+}
+
+func (writer *RecordWriterDKVP2) Write(
+	outrec *types.Mlrmap,
+	ostream *bufio.Writer,
+) {
+	// End of record stream: nothing special for this output format
+	if outrec == nil {
+		return
+	}
+
+	for pe := outrec.Head; pe != nil; pe = pe.Next {
+		ostream.WriteString(pe.Key)
+		ostream.WriteString(writer.writerOptions.OPS)
+		ostream.WriteString(pe.Value.String())
+		if pe.Next != nil {
+			ostream.WriteString(writer.writerOptions.OFS)
+		}
+	}
+	ostream.WriteString(writer.writerOptions.ORS)
+	if !writer.buffer {
+		ostream.Flush()
+	}
+}
+
+// The time.After adds too much overhead, even when there is data
+// available very quickly and the timeout is never reached. :(
+//select {
+//case line, more = <-linesChannel:
+//	if !more {
+//		done = true
+//		break
+//	}
+//case <-time.After(5 * time.Second):
+//	fmt.Println("WAIT")
+//	continue
+//}
diff --git a/cmd/mprof2/main.go b/cmd/mprof2/main.go
new file mode 100644
index 000000000..2b6b0f04c
--- /dev/null
+++ b/cmd/mprof2/main.go
@@ -0,0 +1,382 @@
+// Experiments in performance/profiling.
+package main
+
+import (
+	"bufio"
+	"container/list"
+	"fmt"
+	"io"
+	"os"
+	"runtime"
+	"runtime/debug"
+	"runtime/pprof"
+	"strconv"
+	"strings"
+	//"time"
+
+	"github.com/pkg/profile" // for trace.out
+
+	"github.com/johnkerl/miller/internal/pkg/cli"
+	"github.com/johnkerl/miller/internal/pkg/input"
+	"github.com/johnkerl/miller/internal/pkg/lib"
+	"github.com/johnkerl/miller/internal/pkg/types"
+)
+
+func main() {
+
+	// Respect env $GOMAXPROCS, if provided, else set default.
+	haveSetGoMaxProcs := false
+	goMaxProcsString := os.Getenv("GOMAXPROCS")
+	if goMaxProcsString != "" {
+		goMaxProcs, err := strconv.Atoi(goMaxProcsString)
+		if err != nil {
+			runtime.GOMAXPROCS(goMaxProcs)
+			haveSetGoMaxProcs = true
+		}
+	}
+	if !haveSetGoMaxProcs {
+		// As of Go 1.16 this is the default anyway. For 1.15 and below we need
+		// to explicitly set this.
+		runtime.GOMAXPROCS(runtime.NumCPU())
+	}
+
+	debug.SetGCPercent(500) // Empirical: See README-profiling.md
+
+	if os.Getenv("MPROF_PPROF") != "" {
+		// profiling with cpu.pprof and go tool pprof -http=:8080 cpu.pprof
+		profFilename := "cpu.pprof"
+		handle, err := os.Create(profFilename)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, os.Args[0], ": ", "Could not start CPU profile: ", err)
+			return
+		}
+		defer handle.Close()
+
+		if err := pprof.StartCPUProfile(handle); err != nil {
+			fmt.Fprintln(os.Stderr, os.Args[0], ": ", "Could not start CPU profile: ", err)
+			return
+		}
+		defer pprof.StopCPUProfile()
+
+		fmt.Fprintf(os.Stderr, "CPU profile started.\n")
+		fmt.Fprintf(os.Stderr, "go tool pprof -http=:8080 cpu.pprof\n")
+		defer fmt.Fprintf(os.Stderr, "CPU profile finished.\n")
+	}
+
+	if os.Getenv("MPROF_TRACE") != "" {
+		// tracing with trace.out and go tool trace trace.out
+		fmt.Fprintf(os.Stderr, "go tool trace trace.out\n")
+		defer profile.Start(profile.TraceProfile, profile.ProfilePath(".")).Stop()
+	}
+
+	options := cli.DefaultOptions()
+	types.SetInferrerStringOnly()
+
+	filenames := os.Args[1:]
+	lib.InternalCodingErrorIf(len(filenames) != 1)
+	filename := filenames[0]
+
+	err := Stream(filename, options, os.Stdout)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "mlr: %v.\n", err)
+		os.Exit(1)
+	}
+}
+
+func getBatchSize() int {
+	return 1000
+}
+
+// ================================================================
+type IRecordReader interface {
+	Read(ioChannel chan<- *list.List) error
+}
+
+func Stream(
+	filename string,
+	options *cli.TOptions,
+	outputStream io.WriteCloser,
+) error {
+	initialContext := types.NewContext()
+
+	// Instantiate the record-reader
+	recordReader, err := NewRecordReaderDKVPChanPipelined(&options.ReaderOptions, filename, initialContext)
+	if err != nil {
+		return err
+	}
+
+	// Instantiate the record-writer
+	recordWriter, err := NewRecordWriterDKVP2(&options.WriterOptions)
+	if err != nil {
+		return err
+	}
+
+	ostream := bufio.NewWriter(os.Stdout)
+	defer ostream.Flush()
+
+	ioChannel := make(chan *list.List, 1)
+	errorChannel := make(chan error, 1)
+	doneWritingChannel := make(chan bool, 1)
+
+	go recordReader.Read(ioChannel)
+	go ChannelWriter(ioChannel, recordWriter, doneWritingChannel, ostream)
+
+	done := false
+	for !done {
+		select {
+		case err := <-errorChannel:
+			////fmt.Fprintf(os.Stderr, "ECHAN READ\n")
+			fmt.Fprintln(os.Stderr, "mlr", ": ", err)
+			os.Exit(1)
+		case _ = <-doneWritingChannel:
+			////fmt.Fprintf(os.Stderr, "ZCHAN READ\n")
+			done = true
+			break
+		}
+	}
+
+	return nil
+}
+
+// ================================================================
+
+type RecordReaderDKVPChanPipelined struct {
+	readerOptions  *cli.TReaderOptions
+	filename       string
+	initialContext *types.Context
+}
+
+func NewRecordReaderDKVPChanPipelined(
+	readerOptions *cli.TReaderOptions,
+	filename string,
+	initialContext *types.Context,
+) (*RecordReaderDKVPChanPipelined, error) {
+	return &RecordReaderDKVPChanPipelined{
+		readerOptions:  readerOptions,
+		filename:       filename,
+		initialContext: initialContext,
+	}, nil
+}
+
+func (reader *RecordReaderDKVPChanPipelined) Read(
+	inputChannel chan<- *list.List,
+) error {
+	handle, err := lib.OpenFileForRead(
+		reader.filename,
+		reader.readerOptions.Prepipe,
+		reader.readerOptions.PrepipeIsRaw,
+		reader.readerOptions.FileInputEncoding,
+	)
+	if err != nil {
+		return err
+	} else {
+		reader.processHandle(handle, reader.filename, reader.initialContext, inputChannel)
+		handle.Close()
+	}
+
+	eom := types.NewEndOfStreamMarker(reader.initialContext)
+	leom := list.New()
+	leom.PushBack(eom)
+	inputChannel <- leom
+	////fmt.Fprintf(os.Stderr, "IOCHAN WRITE EOM\n")
+	return nil
+}
+
+func chanProvider(
+	lineScanner *bufio.Scanner,
+	linesChannel chan<- string,
+) {
+	for lineScanner.Scan() {
+		linesChannel <- lineScanner.Text()
+	}
+	close(linesChannel) // end-of-stream marker
+}
+
+// TODO: comment copiously we're trying to handle slow/fast/short/long
+// reads: tail -f, smallfile, bigfile.
+func (reader *RecordReaderDKVPChanPipelined) getRecordBatch(
+	linesChannel <-chan string,
+	maxBatchSize int,
+	context *types.Context,
+) (
+	recordsAndContexts *list.List,
+	eof bool,
+) {
+	//fmt.Printf("GRB ENTER\n")
+	recordsAndContexts = list.New()
+	eof = false
+
+	for i := 0; i < maxBatchSize; i++ {
+		//fmt.Fprintf(os.Stderr, "-- %d/%d %d/%d\n", i, maxBatchSize, len(linesChannel), cap(linesChannel))
+		if len(linesChannel) == 0 && i > 0 {
+			//fmt.Println(" .. BREAK")
+			break
+		}
+		//fmt.Println(" .. B:BLOCK")
+		line, more := <-linesChannel
+		//fmt.Printf(" .. E:BLOCK <<%s>> %v\n", line, more)
+		if !more {
+			eof = true
+			break
+		}
+
+		record := reader.recordFromDKVPLine(line)
+		context.UpdateForInputRecord()
+		recordAndContext := types.NewRecordAndContext(record, context)
+		recordsAndContexts.PushBack(recordAndContext)
+	}
+
+	//fmt.Printf("GRB EXIT\n")
+	return recordsAndContexts, eof
+}
+
+func (reader *RecordReaderDKVPChanPipelined) processHandle(
+	handle io.Reader,
+	filename string,
+	context *types.Context,
+	inputChannel chan<- *list.List,
+) {
+	context.UpdateForStartOfFile(filename)
+	m := getBatchSize()
+
+	lineScanner := input.NewLineScanner(handle, reader.readerOptions.IRS)
+	linesChannel := make(chan string, m)
+	go chanProvider(lineScanner, linesChannel)
+
+	eof := false
+	for !eof {
+		var recordsAndContexts *list.List
+		recordsAndContexts, eof = reader.getRecordBatch(linesChannel, m, context)
+		//fmt.Fprintf(os.Stderr, "GOT RECORD BATCH OF LENGTH %d\n", recordsAndContexts.Len())
+		inputChannel <- recordsAndContexts
+	}
+}
+
+func (reader *RecordReaderDKVPChanPipelined) recordFromDKVPLine(
+	line string,
+) *types.Mlrmap {
+	record := types.NewMlrmap()
+
+	var pairs []string
+	if reader.readerOptions.IFSRegex == nil { // e.g. --no-ifs-regex
+		pairs = lib.SplitString(line, reader.readerOptions.IFS)
+	} else {
+		pairs = lib.RegexSplitString(reader.readerOptions.IFSRegex, line, -1)
+	}
+
+	for i, pair := range pairs {
+		var kv []string
+		if reader.readerOptions.IPSRegex == nil { // e.g. --no-ips-regex
+			kv = strings.SplitN(line, reader.readerOptions.IPS, 2)
+		} else {
+			kv = lib.RegexSplitString(reader.readerOptions.IPSRegex, pair, 2)
+		}
+
+		if len(kv) == 0 {
+			// Ignore. This is expected when splitting with repeated IFS.
+		} else if len(kv) == 1 {
+			// E.g the pair has no equals sign: "a" rather than "a=1" or
+			// "a=".  Here we use the positional index as the key. This way
+			// DKVP is a generalization of NIDX.
+			key := strconv.Itoa(i + 1) // Miller userspace indices are 1-up
+			value := types.MlrvalFromInferredTypeForDataFiles(kv[0])
+			record.PutReference(key, value)
+		} else {
+			key := kv[0]
+			value := types.MlrvalFromInferredTypeForDataFiles(kv[1])
+			record.PutReference(key, value)
+		}
+	}
+	return record
+}
+
+// ================================================================
+func ChannelWriter(
+	outputChannel <-chan *list.List,
+	recordWriter *RecordWriterDKVP2,
+	doneChannel chan<- bool,
+	ostream *bufio.Writer,
+) {
+	for {
+		recordsAndContexts := <-outputChannel
+		if recordsAndContexts != nil {
+			//fmt.Fprintf(os.Stderr, "IOCHAN READ BATCH LEN %d\n", recordsAndContexts.Len())
+		}
+		if recordsAndContexts == nil {
+			//fmt.Fprintf(os.Stderr, "IOCHAN READ EOS\n")
+			doneChannel <- true
+			break
+		}
+
+		for e := recordsAndContexts.Front(); e != nil; e = e.Next() {
+			recordAndContext := e.Value.(*types.RecordAndContext)
+
+			// Three things can come through:
+			// * End-of-stream marker
+			// * Non-nil records to be printed
+			// * Strings to be printed from put/filter DSL print/dump/etc
+			//   statements. They are handled here rather than fmt.Println directly
+			//   in the put/filter handlers since we want all print statements and
+			//   record-output to be in the same goroutine, for deterministic
+			//   output ordering.
+			if !recordAndContext.EndOfStream {
+				record := recordAndContext.Record
+				if record != nil {
+					recordWriter.Write(record, ostream)
+				}
+
+				outputString := recordAndContext.OutputString
+				if outputString != "" {
+					fmt.Print(outputString)
+				}
+
+			} else {
+				// Let the record-writers drain their output, if they have any
+				// queued up. For example, PPRINT needs to see all same-schema
+				// records before printing any, since it needs to compute max width
+				// down columns.
+				recordWriter.Write(nil, ostream)
+				doneChannel <- true
+				////fmt.Fprintf(os.Stderr, "ZCHAN WRITE\n")
+				return
+			}
+		}
+	}
+}
+
+// ================================================================
+
+type RecordWriterDKVP2 struct {
+	writerOptions *cli.TWriterOptions
+	buffer        bool
+}
+
+func NewRecordWriterDKVP2(writerOptions *cli.TWriterOptions) (*RecordWriterDKVP2, error) {
+	return &RecordWriterDKVP2{
+		writerOptions: writerOptions,
+		buffer:        true,
+	}, nil
+}
+
+func (writer *RecordWriterDKVP2) Write(
+	outrec *types.Mlrmap,
+	ostream *bufio.Writer,
+) {
+	// End of record stream: nothing special for this output format
+	if outrec == nil {
+		return
+	}
+
+	for pe := outrec.Head; pe != nil; pe = pe.Next {
+		ostream.WriteString(pe.Key)
+		ostream.WriteString(writer.writerOptions.OPS)
+		ostream.WriteString(pe.Value.String())
+		if pe.Next != nil {
+			ostream.WriteString(writer.writerOptions.OFS)
+		}
+	}
+	ostream.WriteString(writer.writerOptions.ORS)
+	if !writer.buffer {
+		ostream.Flush()
+	}
+}