Greatly reduce the metrics vmstat returns by default.

Vmstat has over 100 fields, most of which are highly
detailed debug information. Trim this down to only
essential fields by default, configurable by flag.

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

collector/vmstat_linux.go

@@ -19,17 +19,25 @@ import (
 	"bufio"
 	"fmt"
 	"os"
+	"regexp"
 	"strconv"
 	"strings"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"gopkg.in/alecthomas/kingpin.v2"
 )
 
 const (
 	vmStatSubsystem = "vmstat"
 )
 
-type vmStatCollector struct{}
+var (
+	vmStatFields = kingpin.Flag("collector.vmstat.fields", "Regexp of fields to return for vmstat collector.").Default("^(pgpg|pswp|pg.*fault|oom_kill).*").String()
+)
+
+type vmStatCollector struct {
+	fieldPattern *regexp.Regexp
+}
 
 func init() {
 	registerCollector("vmstat", defaultEnabled, NewvmStatCollector)
@@ -37,7 +45,10 @@ func init() {
 
 // NewvmStatCollector returns a new Collector exposing vmstat stats.
 func NewvmStatCollector() (Collector, error) {
-	return &vmStatCollector{}, nil
+	pattern := regexp.MustCompile(*vmStatFields)
+	return &vmStatCollector{
+		fieldPattern: pattern,
+	}, nil
 }
 
 func (c *vmStatCollector) Update(ch chan<- prometheus.Metric) error {
@@ -54,6 +65,9 @@ func (c *vmStatCollector) Update(ch chan<- prometheus.Metric) error {
 		if err != nil {
 			return err
 		}
+		if !c.fieldPattern.MatchString(parts[0]) {
+			continue
+		}
 
 		ch <- prometheus.MustNewConstMetric(
 			prometheus.NewDesc(