memory: substract zfs arc cache from used memory

Author: bbedward

go.mod

@@ -54,7 +54,7 @@ require (
 	github.com/tklauser/numcpus v0.11.0 // indirect
 	github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e // indirect
 	github.com/yusufpapurcu/wmi v1.2.4 // indirect
-	golang.org/x/exp v0.0.0-20260211191109-2735e65f0518 // indirect
+	golang.org/x/exp v0.0.0-20260212183809-81e46e3db34a // indirect
 	golang.org/x/sys v0.41.0 // indirect
 	golang.org/x/text v0.34.0 // indirect
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect

go.sum

@@ -102,8 +102,8 @@ github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e/go.mod h1:RbqR21r5mrJu
 github.com/yusufpapurcu/wmi v1.2.4 h1:zFUKzehAFReQwLys1b/iSMl+JQGSCSjtVqQn9bBrPo0=
 github.com/yusufpapurcu/wmi v1.2.4/go.mod h1:SBZ9tNy3G9/m5Oi98Zks0QjeHVDvuK0qfxQmPyzfmi0=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
-golang.org/x/exp v0.0.0-20260211191109-2735e65f0518 h1:2E1CW7v5QB+Wi3N+MXllOtVR6SFmI8iJM8EdzgxrgrU=
-golang.org/x/exp v0.0.0-20260211191109-2735e65f0518/go.mod h1:K79w1Vqn7PoiZn+TkNpx3BUWUQksGO3JcVX6qIjytmA=
+golang.org/x/exp v0.0.0-20260212183809-81e46e3db34a h1:ovFr6Z0MNmU7nH8VaX5xqw+05ST2uO1exVfZPVqRC5o=
+golang.org/x/exp v0.0.0-20260212183809-81e46e3db34a/go.mod h1:K79w1Vqn7PoiZn+TkNpx3BUWUQksGO3JcVX6qIjytmA=
 golang.org/x/net v0.50.0 h1:ucWh9eiCGyDR3vtzso0WMQinm2Dnt8cFMuQa9K33J60=
 golang.org/x/net v0.50.0/go.mod h1:UgoSli3F/pBgdJBHCTc+tp3gmrU4XswgGRgtnwWTfyM=
 golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=

gops/memory.go

@@ -1,6 +1,11 @@
 package gops
 
 import (
+	"bufio"
+	"os"
+	"strconv"
+	"strings"
+
 	"github.com/AvengeMedia/dgop/models"
 )
 
@@ -16,10 +21,26 @@ func (self *GopsUtil) GetMemoryInfo() (*models.MemoryInfo, error) {
 	cached := v.Cached / 1024
 	sreclaimable := v.Sreclaimable / 1024
 	shared := v.Shared / 1024
+	available := v.Available / 1024
 
 	// gopsutil Cached includes SReclaimable, get raw value
 	rawCached := cached - sreclaimable
 
+	// ZFS ARC is reclaimable cache not reflected in /proc/meminfo.
+	// Read it from /proc/spl/kstat/zfs/arcstats (same approach as btop).
+	arcSize, arcMin := readZfsArcStats()
+	arcSizeKB := arcSize / 1024
+	arcMinKB := arcMin / 1024
+
+	var freeableArc uint64
+	switch {
+	case arcSizeKB > arcMinKB:
+		freeableArc = arcSizeKB - arcMinKB
+	}
+
+	rawCached += arcSizeKB
+	available += freeableArc
+
 	// Used = Total - Free - Cached - SReclaimable - Buffers + Shared
 	usedDiff := free + rawCached + sreclaimable + buffers
 	var used uint64
@@ -40,12 +61,38 @@ func (self *GopsUtil) GetMemoryInfo() (*models.MemoryInfo, error) {
 		Used:         used,
 		UsedPercent:  usedPercent,
 		Free:         free,
-		Available:    v.Available / 1024,
+		Available:    available,
 		Buffers:      buffers,
 		Cached:       rawCached,
 		SReclaimable: sreclaimable,
 		Shared:       shared,
+		ZfsArcSize:   arcSizeKB,
 		SwapTotal:    v.SwapTotal / 1024,
 		SwapFree:     v.SwapFree / 1024,
 	}, nil
 }
+
+// readZfsArcStats reads ARC size and c_min from /proc/spl/kstat/zfs/arcstats.
+// Returns (0, 0) if ZFS is not present.
+func readZfsArcStats() (size uint64, cMin uint64) {
+	f, err := os.Open("/proc/spl/kstat/zfs/arcstats")
+	if err != nil {
+		return 0, 0
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) != 3 {
+			continue
+		}
+		switch fields[0] {
+		case "size":
+			size, _ = strconv.ParseUint(fields[2], 10, 64)
+		case "c_min":
+			cMin, _ = strconv.ParseUint(fields[2], 10, 64)
+		}
+	}
+	return size, cMin
+}

models/memory.go

@@ -10,6 +10,7 @@ type MemoryInfo struct {
 	Cached       uint64  `json:"cached"`
 	SReclaimable uint64  `json:"sreclaimable"`
 	Shared       uint64  `json:"shared"`
+	ZfsArcSize   uint64  `json:"zfsArcSize"`
 	SwapTotal    uint64  `json:"swaptotal"`
 	SwapFree     uint64  `json:"swapfree"`
 }