From af4877ca300346ee7d4a0c3d4cc26de605d446c0 Mon Sep 17 00:00:00 2001
From: Henry Dollman <hank@henrygd.me>
Date: Sat, 5 Oct 2024 15:29:27 -0400
Subject: [PATCH] add MEM_CALC env var

---
 beszel/internal/agent/agent.go  |  2 ++
 beszel/internal/agent/system.go | 17 +++++++++++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/beszel/internal/agent/agent.go b/beszel/internal/agent/agent.go
index ac35dc3..4244fcc 100644
--- a/beszel/internal/agent/agent.go
+++ b/beszel/internal/agent/agent.go
@@ -13,6 +13,7 @@ import (
 
 type Agent struct {
 	debug            bool                       // true if LOG_LEVEL is set to debug
+	memCalc          string                     // Memory calculation formula
 	fsNames          []string                   // List of filesystem device names being monitored
 	fsStats          map[string]*system.FsStats // Keeps track of disk stats for each filesystem
 	netInterfaces    map[string]struct{}        // Stores all valid network interfaces
@@ -26,6 +27,7 @@ type Agent struct {
 func NewAgent() *Agent {
 	return &Agent{
 		sensorsContext: context.Background(),
+		memCalc:        os.Getenv("MEM_CALC"),
 	}
 }
 
diff --git a/beszel/internal/agent/system.go b/beszel/internal/agent/system.go
index fe0dc27..7cee4d3 100644
--- a/beszel/internal/agent/system.go
+++ b/beszel/internal/agent/system.go
@@ -52,12 +52,21 @@ func (a *Agent) getSystemStats() system.Stats {
 
 	// memory
 	if v, err := mem.VirtualMemory(); err == nil {
+		// cache + buffers value for default mem calculation
+		cacheBuff := v.Total - v.Free - v.Used
+		// htop memory calculation overrides
+		if a.memCalc == "htop" {
+			// note: gopsutil automatically adds SReclaimable to v.Cached
+			cacheBuff = v.Cached + v.Buffers - v.Shared
+			v.Used = v.Total - (v.Free + cacheBuff)
+			v.UsedPercent = float64(v.Used) / float64(v.Total) * 100.0
+		}
 		systemStats.Mem = bytesToGigabytes(v.Total)
-		systemStats.MemUsed = bytesToGigabytes(v.Used)
-		systemStats.MemBuffCache = bytesToGigabytes(v.Total - v.Free - v.Used)
-		systemStats.MemPct = twoDecimals(v.UsedPercent)
 		systemStats.Swap = bytesToGigabytes(v.SwapTotal)
-		systemStats.SwapUsed = bytesToGigabytes(v.SwapTotal - v.SwapFree)
+		systemStats.SwapUsed = bytesToGigabytes(v.SwapTotal - v.SwapFree - v.SwapCached)
+		systemStats.MemBuffCache = bytesToGigabytes(cacheBuff)
+		systemStats.MemUsed = bytesToGigabytes(v.Used)
+		systemStats.MemPct = twoDecimals(v.UsedPercent)
 	}
 
 	// disk usage