From d11d48c7a89b71869a343a1f1dc41e6d5078aaa4 Mon Sep 17 00:00:00 2001
From: Ben Kochie <superq@gmail.com>
Date: Wed, 10 Feb 2021 13:38:28 +0100
Subject: [PATCH] Default GOMAXPROCS to 1

Avoid running on all CPUs by limiting the Go runtime to one CPU by
default. Avoids having Go routines schedule on every CPU, driving up the
visible run queue length on high CPU count systems.

https://github.com/prometheus/node_exporter/issues/1880

Signed-off-by: Ben Kochie <superq@gmail.com>
---
 CHANGELOG.md     | 2 ++
 node_exporter.go | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7e7d109d39..b678b119d5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,8 @@
 * [ENHANCEMENT]
 * [BUGFIX]
 
+* [CHANGE] Default GOMAXPROCS to 1
+
 ## 1.1.0 / 2021-02-05
 
 NOTE: We have improved some of the flag naming conventions (PR #1743). The old names are
diff --git a/node_exporter.go b/node_exporter.go
index 2347a49076..6db7acbad3 100644
--- a/node_exporter.go
+++ b/node_exporter.go
@@ -19,6 +19,7 @@ import (
 	_ "net/http/pprof"
 	"os"
 	"os/user"
+	"runtime"
 	"sort"
 
 	"github.com/prometheus/common/promlog"
@@ -163,6 +164,9 @@ func main() {
 			"web.config",
 			"[EXPERIMENTAL] Path to config yaml file that can enable TLS or authentication.",
 		).Default("").String()
+		maxProcs = kingpin.Flag(
+			"runtime.gomaxprocs", "The target number of CPUs Go will run on (GOMAXPROCS)",
+		).Envar("GOMAXPROCS").Default("1").Int()
 	)
 
 	promlogConfig := &promlog.Config{}
@@ -180,6 +184,8 @@ func main() {
 	if user, err := user.Current(); err == nil && user.Uid == "0" {
 		level.Warn(logger).Log("msg", "Node Exporter is running as root user. This exporter is designed to run as unpriviledged user, root is not required.")
 	}
+	runtime.GOMAXPROCS(*maxProcs)
+	level.Debug(logger).Log("msg", "Go MAXPROCS", "procs", *maxProcs)
 
 	http.Handle(*metricsPath, newHandler(!*disableExporterMetrics, *maxRequests, logger))
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {