From c25b839078eaa6d8f4b8ac491223b7283e6aef13 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Thu, 1 Jul 2021 11:49:16 +0300
Subject: [PATCH] lib/workingsetcache: reset the cache mode when the cache is
 reset

This should reduce memory usage if the working set is reduced after the cache reset.
---
 docs/CHANGELOG.md            | 2 ++
 lib/workingsetcache/cache.go | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 5cdf685fe..4ba8aff55 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -6,6 +6,8 @@ sort: 15
 
 ## tip
 
+* FEATURE: reduce memory usage when performing heavy queries over high number of time series.
+
 * BUGFIX: remove `{ %space %}` typo in `/targets` output. The typo has been introduced in v1.62.0. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1408).
 
 
diff --git a/lib/workingsetcache/cache.go b/lib/workingsetcache/cache.go
index c21a331bd..03d1ce1d8 100644
--- a/lib/workingsetcache/cache.go
+++ b/lib/workingsetcache/cache.go
@@ -218,6 +218,8 @@ func (c *Cache) Reset() {
 	prev.Reset()
 	curr := c.curr.Load().(*fastcache.Cache)
 	curr.Reset()
+	// Reset the mode to `split` in the hope the working set size becomes smaller after the reset.
+	atomic.StoreUint64(&c.mode, split)
 }
 
 // UpdateStats updates fcs with cache stats.