From 7b33bc67a19f1cb5cc32550c53a9a536aca451f0 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Thu, 27 May 2021 21:57:31 +0300
Subject: [PATCH] lib/mergeset: remove a pool for inmemoryBlock structs

The pool for inmemoryBlock struct doesn't give any performance gains in production workloads,
while it may result in excess memory usage for inmemoryBlock structs inside the pool during
background merge of indexdb.
---
 lib/mergeset/encoding.go    | 15 ++-------------
 lib/mergeset/part_search.go |  2 +-
 lib/mergeset/table.go       |  9 ++++-----
 3 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/lib/mergeset/encoding.go b/lib/mergeset/encoding.go
index 8cb57082cf..f57f4f4e3f 100644
--- a/lib/mergeset/encoding.go
+++ b/lib/mergeset/encoding.go
@@ -540,17 +540,6 @@ func putLensBuffer(lb *lensBuffer) {
 	lensBufferPool.Put(lb)
 }
 
-func getInmemoryBlock() *inmemoryBlock {
-	v := ibPool.Get()
-	if v == nil {
-		return &inmemoryBlock{}
-	}
-	return v.(*inmemoryBlock)
+func newInmemoryBlock() *inmemoryBlock {
+	return &inmemoryBlock{}
 }
-
-func putInmemoryBlock(ib *inmemoryBlock) {
-	ib.Reset()
-	ibPool.Put(ib)
-}
-
-var ibPool sync.Pool
diff --git a/lib/mergeset/part_search.go b/lib/mergeset/part_search.go
index 8671561b63..d2a8a1116c 100644
--- a/lib/mergeset/part_search.go
+++ b/lib/mergeset/part_search.go
@@ -316,7 +316,7 @@ func (ps *partSearch) readInmemoryBlock(bh *blockHeader) (*inmemoryBlock, error)
 	ps.sb.lensData = bytesutil.Resize(ps.sb.lensData, int(bh.lensBlockSize))
 	ps.p.lensFile.MustReadAt(ps.sb.lensData, int64(bh.lensBlockOffset))
 
-	ib := getInmemoryBlock()
+	ib := newInmemoryBlock()
 	if err := ib.UnmarshalData(&ps.sb, bh.firstItem, bh.commonPrefix, bh.itemsCount, bh.marshalType); err != nil {
 		return nil, fmt.Errorf("cannot unmarshal storage block with %d items: %w", bh.itemsCount, err)
 	}
diff --git a/lib/mergeset/table.go b/lib/mergeset/table.go
index ba12ada94c..6a9eb7bed1 100644
--- a/lib/mergeset/table.go
+++ b/lib/mergeset/table.go
@@ -182,16 +182,15 @@ func (ris *rawItemsShard) addItems(tb *Table, items [][]byte) error {
 	ris.mu.Lock()
 	ibs := ris.ibs
 	if len(ibs) == 0 {
-		ib := getInmemoryBlock()
+		ib := newInmemoryBlock()
 		ibs = append(ibs, ib)
 		ris.ibs = ibs
 	}
 	ib := ibs[len(ibs)-1]
 	for _, item := range items {
 		if !ib.Add(item) {
-			ib = getInmemoryBlock()
+			ib = newInmemoryBlock()
 			if !ib.Add(item) {
-				putInmemoryBlock(ib)
 				err = fmt.Errorf("cannot insert an item %q into an empty inmemoryBlock; it looks like the item is too large? len(item)=%d", item, len(item))
 				break
 			}
@@ -675,13 +674,13 @@ func (tb *Table) mergeRawItemsBlocks(blocksToMerge []*inmemoryBlock) {
 func (tb *Table) mergeInmemoryBlocks(blocksToMerge []*inmemoryBlock) *partWrapper {
 	// Convert blocksToMerge into inmemoryPart's
 	mps := make([]*inmemoryPart, 0, len(blocksToMerge))
-	for _, ib := range blocksToMerge {
+	for i, ib := range blocksToMerge {
 		if len(ib.items) == 0 {
 			continue
 		}
 		mp := getInmemoryPart()
 		mp.Init(ib)
-		putInmemoryBlock(ib)
+		blocksToMerge[i] = nil
 		mps = append(mps, mp)
 	}
 	if len(mps) == 0 {