NetBSD support for the meminfo collector

This depends on a recent change to golang.org/x/sys that adds a
unix.SysctlUvmexp function.

Signed-off-by: Benny Siegert <bsiegert@gmail.com>

collector/meminfo.go

@@ -11,8 +11,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build (darwin || linux || openbsd) && !nomeminfo
+//go:build (darwin || linux || openbsd || netbsd) && !nomeminfo
-// +build darwin linux openbsd
+// +build darwin linux openbsd netbsd
 // +build !nomeminfo
 
 package collector

collector/meminfo_netbsd.go

@@ -0,0 +1,43 @@
+// Copyright 2023 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build netbsd && !nomeminfo
+// +build netbsd,!nomeminfo
+
+package collector
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+func (c *meminfoCollector) getMemInfo() (map[string]float64, error) {
+	uvmexp, err := unix.SysctlUvmexp("vm.uvmexp2")
+	if err != nil {
+		return nil, err
+	}
+
+	ps := float64(uvmexp.Pagesize)
+
+	// see uvm(9)
+	return map[string]float64{
+		"active_bytes":                  ps * float64(uvmexp.Active),
+		"free_bytes":                    ps * float64(uvmexp.Free),
+		"inactive_bytes":                ps * float64(uvmexp.Inactive),
+		"size_bytes":                    ps * float64(uvmexp.Npages),
+		"swap_size_bytes":               ps * float64(uvmexp.Swpages),
+		"swap_used_bytes":               ps * float64(uvmexp.Swpginuse),
+		"swapped_in_pages_bytes_total":  ps * float64(uvmexp.Pgswapin),
+		"swapped_out_pages_bytes_total": ps * float64(uvmexp.Pgswapout),
+		"wired_bytes":                   ps * float64(uvmexp.Wired),
+	}, nil
+}