From 377bb06b4744f5423fb5c567959814b77409f777 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Mon, 5 Jul 2021 12:31:26 +0300
Subject: [PATCH] lib/cgroup: set GOGC to 50 by default if it isn't set

This should reduce memory usage for typical VictoriaMetrics workloads by up to 50%
---
 lib/cgroup/cpu.go         |  6 +++---
 lib/cgroup/mem.go         | 30 ++++++++++++++++++++++++++++++
 lib/httpserver/metrics.go |  1 +
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/lib/cgroup/cpu.go b/lib/cgroup/cpu.go
index b151aa925..46c706099 100644
--- a/lib/cgroup/cpu.go
+++ b/lib/cgroup/cpu.go
@@ -7,16 +7,16 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
-	"sync"
 )
 
 // AvailableCPUs returns the number of available CPU cores for the app.
 func AvailableCPUs() int {
-	availableCPUsOnce.Do(updateGOMAXPROCSToCPUQuota)
 	return runtime.GOMAXPROCS(-1)
 }
 
-var availableCPUsOnce sync.Once
+func init() {
+	updateGOMAXPROCSToCPUQuota()
+}
 
 // updateGOMAXPROCSToCPUQuota updates GOMAXPROCS to cgroup CPU quota if GOMAXPROCS isn't set in environment var.
 func updateGOMAXPROCSToCPUQuota() {
diff --git a/lib/cgroup/mem.go b/lib/cgroup/mem.go
index c4641a4b8..2fa34a11a 100644
--- a/lib/cgroup/mem.go
+++ b/lib/cgroup/mem.go
@@ -1,9 +1,39 @@
 package cgroup
 
 import (
+	"os"
+	"runtime/debug"
 	"strconv"
 )
 
+// GetGOGC returns GOGC value for the currently running process.
+//
+// See https://golang.org/pkg/runtime/#hdr-Environment_Variables for more details about GOGC
+func GetGOGC() int {
+	return gogc
+}
+
+func init() {
+	initGOGC()
+}
+
+func initGOGC() {
+	if v := os.Getenv("GOGC"); v != "" {
+		n, err := strconv.Atoi(v)
+		if err != nil {
+			n = 100
+		}
+		gogc = n
+	} else {
+		// Set GOGC to 50% by default if it isn't set yet.
+		// This should reduce memory usage for typical workloads for VictoriaMetrics components.
+		gogc = 50
+		debug.SetGCPercent(gogc)
+	}
+}
+
+var gogc int
+
 // GetMemoryLimit returns cgroup memory limit
 func GetMemoryLimit() int64 {
 	// Try determining the amount of memory inside docker container.
diff --git a/lib/httpserver/metrics.go b/lib/httpserver/metrics.go
index a14603710..0b822f5d5 100644
--- a/lib/httpserver/metrics.go
+++ b/lib/httpserver/metrics.go
@@ -51,6 +51,7 @@ func writePrometheusMetrics(w io.Writer) {
 	fmt.Fprintf(w, "vm_allowed_memory_bytes %d\n", memory.Allowed())
 	fmt.Fprintf(w, "vm_available_memory_bytes %d\n", memory.Allowed()+memory.Remaining())
 	fmt.Fprintf(w, "vm_available_cpu_cores %d\n", cgroup.AvailableCPUs())
+	fmt.Fprintf(w, "vm_gogc %d\n", cgroup.GetGOGC())
 
 	// Export start time and uptime in seconds
 	fmt.Fprintf(w, "vm_app_start_timestamp %d\n", startTime.Unix())