From 4e71914e3cfdd4cf8b2379ed52b6d6f4364ba747 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@victoriametrics.com>
Date: Sun, 12 Mar 2023 00:42:17 -0800
Subject: [PATCH] app/vmselect/netstorage: do not intern string representation
 of MetricName for time series received from vmstorage

It has been appeared that this interning may lead to increased memory usage and increased CPU usage
when vmselect performs queries, which select big number of time series.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3692
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3863
---
 app/vmselect/netstorage/netstorage.go | 11 +++++++----
 docs/CHANGELOG.md                     |  3 ++-
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/app/vmselect/netstorage/netstorage.go b/app/vmselect/netstorage/netstorage.go
index ed43a12e3c..4ad34b6a95 100644
--- a/app/vmselect/netstorage/netstorage.go
+++ b/app/vmselect/netstorage/netstorage.go
@@ -1187,8 +1187,10 @@ func ProcessSearchQuery(qt *querytracer.Tracer, sq *storage.SearchQuery, deadlin
 			putStorageSearch(sr)
 			return nil, fmt.Errorf("cannot write %d bytes to temporary file: %w", len(buf), err)
 		}
-		metricName := bytesutil.InternBytes(sr.MetricBlockRef.MetricName)
-		brs := m[metricName]
+		// Do not intern mb.MetricName, since it leads to increased memory usage.
+		// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3692
+		metricName := sr.MetricBlockRef.MetricName
+		brs := m[string(metricName)]
 		if brs == nil {
 			brs = &blockRefs{}
 			brs.brs = brs.brsPrealloc[:0]
@@ -1198,8 +1200,9 @@ func ProcessSearchQuery(qt *querytracer.Tracer, sq *storage.SearchQuery, deadlin
 			addr:    addr,
 		})
 		if len(brs.brs) == 1 {
-			orderedMetricNames = append(orderedMetricNames, metricName)
-			m[metricName] = brs
+			metricNameStr := string(metricName)
+			orderedMetricNames = append(orderedMetricNames, metricNameStr)
+			m[metricNameStr] = brs
 		}
 	}
 	if err := sr.Error(); err != nil {
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index feec47873e..8d6387484d 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -15,7 +15,8 @@ The following tip changes can be tested by building VictoriaMetrics components f
 
 ## v1.87.x long-time support release (LTS)
 
-* BUGFIX: fix a bug, which could lead to incomplete or empty results for heavy queries selecting tens of thousands of time series. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3946).
+* BUGFIX: vmstorage: fix a bug, which could lead to incomplete or empty results for heavy queries selecting tens of thousands of time series. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3946).
+* BUGFIX: vmselect: reduce memory usage and CPU usage when performing heavy queries. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3692).
 * BUGFIX: prevent from possible `invalid memory address or nil pointer dereference` panic during [background merge](https://docs.victoriametrics.com/#storage). The issue has been introduced at [v1.85.0](https://docs.victoriametrics.com/CHANGELOG.html#v1850). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3897).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): do not register `vm_promscrape_config_*` metrics if `-promscrape.config` flag is not used. Previously those metrics were registered and never updated, which was confusing and could trigger false-positive alerts.
 * BUGFIX: [vmctl](https://docs.victoriametrics.com/vmctl.html): skip measurements with no fields when migrating data from influxdb. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3837).