From e84c87750357a289a280acc59a93b44d9d57d646 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@victoriametrics.com>
Date: Fri, 26 Jan 2024 21:33:08 +0100
Subject: [PATCH] lib/mergeset: remove inmemoryBlock pooling, since it wasn't
 effecitve

This should reduce memory usage a bit when new time series are ingested at high rate (aka high churn rate)
---
 lib/mergeset/encoding.go    | 24 ------------------------
 lib/mergeset/part_search.go |  2 +-
 lib/mergeset/table.go       |  6 ++----
 3 files changed, 3 insertions(+), 29 deletions(-)

diff --git a/lib/mergeset/encoding.go b/lib/mergeset/encoding.go
index a4935d4e6..f59bdc58d 100644
--- a/lib/mergeset/encoding.go
+++ b/lib/mergeset/encoding.go
@@ -11,7 +11,6 @@ import (
 	"unsafe"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/encoding"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 )
@@ -571,26 +570,3 @@ func getLensBuffer(n int) *lensBuffer {
 func putLensBuffer(lb *lensBuffer) {
 	lensBufferPool.Put(lb)
 }
-
-func getInmemoryBlock() *inmemoryBlock {
-	select {
-	case ib := <-ibPoolCh:
-		return ib
-	default:
-		return &inmemoryBlock{}
-	}
-}
-
-func putInmemoryBlock(ib *inmemoryBlock) {
-	ib.Reset()
-	select {
-	case ibPoolCh <- ib:
-	default:
-		// drop ib in order to reduce memory usage on systems with big number of CPU cores
-	}
-}
-
-// Every inmemoryBlock struct occupies at least 64KB of memory, e.g. quite big amounts of memory.
-// Use a chan instead of sync.Pool in order to reduce memory usage on systems
-// with big number of CPU cores.
-var ibPoolCh = make(chan *inmemoryBlock, 100*cgroup.AvailableCPUs())
diff --git a/lib/mergeset/part_search.go b/lib/mergeset/part_search.go
index 8ee302a3c..29a0a6723 100644
--- a/lib/mergeset/part_search.go
+++ b/lib/mergeset/part_search.go
@@ -325,7 +325,7 @@ func (ps *partSearch) readInmemoryBlock(bh *blockHeader) (*inmemoryBlock, error)
 	ps.sb.lensData = bytesutil.ResizeNoCopyMayOverallocate(ps.sb.lensData, int(bh.lensBlockSize))
 	ps.p.lensFile.MustReadAt(ps.sb.lensData, int64(bh.lensBlockOffset))
 
-	ib := getInmemoryBlock()
+	ib := &inmemoryBlock{}
 	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 b4e64dbe4..5c692a5ff 100644
--- a/lib/mergeset/table.go
+++ b/lib/mergeset/table.go
@@ -233,7 +233,7 @@ func (ris *rawItemsShard) addItems(tb *Table, items [][]byte) [][]byte {
 	ris.mu.Lock()
 	ibs := ris.ibs
 	if len(ibs) == 0 {
-		ib := getInmemoryBlock()
+		ib := &nmemoryBlock{}
 		ibs = append(ibs, ib)
 		ris.ibs = ibs
 	}
@@ -249,12 +249,11 @@ func (ris *rawItemsShard) addItems(tb *Table, items [][]byte) [][]byte {
 			atomic.StoreUint64(&ris.lastFlushTime, fasttime.UnixTimestamp())
 			break
 		}
-		ib = getInmemoryBlock()
+		ib = &nmemoryBlock{}
 		if ib.Add(item) {
 			ibs = append(ibs, ib)
 			continue
 		}
-		putInmemoryBlock(ib)
 		logger.Panicf("BUG: cannot insert too big item into an empty inmemoryBlock len(item)=%d; the caller should be responsible for avoiding too big items", len(item))
 	}
 	ris.ibs = ibs
@@ -882,7 +881,6 @@ func (tb *Table) createInmemoryPart(ibs []*inmemoryBlock) *partWrapper {
 		}
 		bsr := getBlockStreamReader()
 		bsr.MustInitFromInmemoryBlock(ib)
-		putInmemoryBlock(ib)
 		bsrs = append(bsrs, bsr)
 	}
 	if len(bsrs) == 0 {