Use the GODEBUG env var to disable Transparent Huge Pages (#463)

THP is unhelpful for databases, in general, because memory access tends to be non-contiguous, and the use of THP can make performance worse when it requires a bunch of page defragmentation to load and map a huge page.

We now disable it by default, using the GODEBUG environment variable.

Adds a generic facility for managing GODEBUG clauses to the Helm chart.

closes https://cockroachlabs.atlassian.net/browse/TREQ-888

Author: MattWhelan

build/templates/README.md

@@ -710,3 +710,8 @@ iap:
   # Create Google Cloud OAuth credentials and set client id and secret
   # clientId:
   # clientSecret:
+
+# Set the GODEBUG env var for the Go runtime. By default, disable Transparent Huge Pages,
+# which cause memory inefficiency for CRDB.
+godebug:
+  disablethp: "1"

build/templates/values.yaml

@@ -350,3 +350,14 @@ Validate the WAL failover configuration.
     {{- end -}}
   {{- end -}}
 {{- end -}}
+
+{{/*
+Construct the GODEBUG env var value (looks like: GODEBUG="foo=bar,baz=quux"; default: "disablethp=1")
+*/}}
+{{- define "godebugList" -}}
+{{- $godebugList := list -}}
+{{- range $key, $value := .Values.godebug }}
+  {{- $godebugList = append $godebugList (printf "%s=%s" $key $value) -}}
+{{- end }}
+{{- join "," $godebugList -}}
+{{- end }}

cockroachdb/README.md

@@ -260,6 +260,8 @@ spec:
               value: {{ template "cockroachdb.fullname" . }}.{{ .Release.Namespace }}.svc.{{ .Values.clusterDomain }}
             - name: COCKROACH_CHANNEL
               value: kubernetes-helm
+            - name: GODEBUG
+              value: {{ include "godebugList" . }}
           {{- with .Values.statefulset.env }}
             {{- toYaml . | nindent 12 }}
           {{- end }}

cockroachdb/templates/_helpers.tpl

@@ -711,3 +711,8 @@ iap:
   # Create Google Cloud OAuth credentials and set client id and secret
   # clientId:
   # clientSecret:
+
+# Set the GODEBUG env var for the Go runtime. By default, disable Transparent Huge Pages,
+# which cause memory inefficiency for CRDB.
+godebug:
+  disablethp: "1"