From 2516ab53ab00d22263bb239a2f535a7720a022fc Mon Sep 17 00:00:00 2001
From: Ryan Kim <ryanfsdf@live.ca>
Date: Wed, 3 Jul 2019 14:45:58 -0400
Subject: [PATCH] Remove L0SlowdownThreshold

---
 cmd/pebble/db.go              |  1 -
 db.go                         | 22 +---------------------
 internal/base/options.go      |  8 --------
 internal/base/options_test.go |  1 -
 4 files changed, 1 insertion(+), 31 deletions(-)

diff --git a/cmd/pebble/db.go b/cmd/pebble/db.go
index 6d6093282e4..75153bcea2f 100644
--- a/cmd/pebble/db.go
+++ b/cmd/pebble/db.go
@@ -56,7 +56,6 @@ func newPebbleDB(dir string) DB {
 		MemTableStopWritesThreshold: 4,
 		MinFlushRate:                4 << 20,
 		L0CompactionThreshold:       2,
-		L0SlowdownWritesThreshold:   20,
 		L0StopWritesThreshold:       32,
 		LBaseMaxBytes:               64 << 20, // 64 MB
 		Levels: []pebble.LevelOptions{{
diff --git a/db.go b/db.go
index 06ddad361cb..2d59fdcdeee 100644
--- a/db.go
+++ b/db.go
@@ -8,14 +8,13 @@ package pebble // import "github.com/petermattis/pebble"
 import (
 	"errors"
 	"fmt"
-	"github.com/petermattis/pebble/internal/rate"
 	"io"
 	"sync"
 	"sync/atomic"
-	"time"
 
 	"github.com/petermattis/pebble/internal/arenaskl"
 	"github.com/petermattis/pebble/internal/base"
+	"github.com/petermattis/pebble/internal/rate"
 	"github.com/petermattis/pebble/internal/record"
 	"github.com/petermattis/pebble/vfs"
 )
@@ -399,9 +398,6 @@ func (d *DB) commitApply(b *Batch, mem *memTable) error {
 func (d *DB) commitWrite(b *Batch, wg *sync.WaitGroup) (*memTable, error) {
 	d.mu.Lock()
 
-	// Throttle writes if there are too many L0 tables.
-	d.throttleWrite()
-
 	if b.flushable != nil {
 		b.flushable.seqNum = b.seqNum()
 	}
@@ -797,22 +793,6 @@ func (d *DB) walPreallocateSize() int {
 	return size
 }
 
-func (d *DB) throttleWrite() {
-	if len(d.mu.versions.currentVersion().files[0]) <= d.opts.L0SlowdownWritesThreshold {
-		return
-	}
-	// fmt.Printf("L0 slowdown writes threshold\n")
-	// We are getting close to hitting a hard limit on the number of L0
-	// files. Rather than delaying a single write by several seconds when we hit
-	// the hard limit, start delaying each individual write by 1ms to reduce
-	// latency variance.
-	//
-	// TODO(peter): Use more sophisticated rate limiting.
-	d.mu.Unlock()
-	time.Sleep(1 * time.Millisecond)
-	d.mu.Lock()
-}
-
 func (d *DB) makeRoomForWrite(b *Batch) error {
 	force := b == nil || b.flushable != nil
 	for {
diff --git a/internal/base/options.go b/internal/base/options.go
index e407abec876..cdf489f9022 100644
--- a/internal/base/options.go
+++ b/internal/base/options.go
@@ -247,10 +247,6 @@ type Options struct {
 	// The number of files necessary to trigger an L0 compaction.
 	L0CompactionThreshold int
 
-	// Soft limit on the number of L0 files. Writes are slowed down when this
-	// threshold is reached.
-	L0SlowdownWritesThreshold int
-
 	// Hard limit on the number of L0 files. Writes are stopped when this
 	// threshold is reached.
 	L0StopWritesThreshold int
@@ -340,9 +336,6 @@ func (o *Options) EnsureDefaults() *Options {
 	if o.L0CompactionThreshold <= 0 {
 		o.L0CompactionThreshold = 4
 	}
-	if o.L0SlowdownWritesThreshold <= 0 {
-		o.L0SlowdownWritesThreshold = 8
-	}
 	if o.L0StopWritesThreshold <= 0 {
 		o.L0StopWritesThreshold = 12
 	}
@@ -418,7 +411,6 @@ func (o *Options) String() string {
 	fmt.Fprintf(&buf, "  comparer=%s\n", o.Comparer.Name)
 	fmt.Fprintf(&buf, "  disable_wal=%t\n", o.DisableWAL)
 	fmt.Fprintf(&buf, "  l0_compaction_threshold=%d\n", o.L0CompactionThreshold)
-	fmt.Fprintf(&buf, "  l0_slowdown_writes_threshold=%d\n", o.L0SlowdownWritesThreshold)
 	fmt.Fprintf(&buf, "  l0_stop_writes_threshold=%d\n", o.L0StopWritesThreshold)
 	fmt.Fprintf(&buf, "  lbase_max_bytes=%d\n", o.LBaseMaxBytes)
 	fmt.Fprintf(&buf, "  max_manifest_file_size=%d\n", o.MaxManifestFileSize)
diff --git a/internal/base/options_test.go b/internal/base/options_test.go
index ce7efbb2b21..bab7b649315 100644
--- a/internal/base/options_test.go
+++ b/internal/base/options_test.go
@@ -45,7 +45,6 @@ func TestOptionsString(t *testing.T) {
   comparer=leveldb.BytewiseComparator
   disable_wal=false
   l0_compaction_threshold=4
-  l0_slowdown_writes_threshold=8
   l0_stop_writes_threshold=12
   lbase_max_bytes=67108864
   max_manifest_file_size=134217728