support ZFS ARC on freebsd

agent/zfs/zfs_freebsd.go

@@ -0,0 +1,11 @@
+//go:build freebsd
+
+package zfs
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+func ARCSize() (uint64, error) {
+	return unix.SysctlUint64("kstat.zfs.misc.arcstats.size")
+}

agent/zfs/zfs_linux.go

@@ -0,0 +1,34 @@
+//go:build linux
+
+// Package zfs provides functions to read ZFS statistics.
+package zfs
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func ARCSize() (uint64, error) {
+	file, err := os.Open("/proc/spl/kstat/zfs/arcstats")
+	if err != nil {
+		return 0, err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.HasPrefix(line, "size") {
+			fields := strings.Fields(line)
+			if len(fields) < 3 {
+				return 0, fmt.Errorf("unexpected arcstats size format: %s", line)
+			}
+			return strconv.ParseUint(fields[2], 10, 64)
+		}
+	}
+
+	return 0, fmt.Errorf("size field not found in arcstats")
+}

agent/zfs/zfs_unsupported.go

@@ -0,0 +1,9 @@
+//go:build !linux && !freebsd
+
+package zfs
+
+import "errors"
+
+func ARCSize() (uint64, error) {
+	return 0, errors.ErrUnsupported
+}