Ongoing work on fixing "Insufficient free RAM to start VM" issue

src/qga/qga.go

@@ -3,6 +3,7 @@ package qga
 import (
 	"fmt"
 	"net"
+	"errors"
 	"encoding/base64"
 	"nexus-server/logger"
 )
@@ -38,7 +39,7 @@ func (q *QGACon)SendShutdown() error {
 }
 
 func (q *QGACon)WriteFile(filePath string) error {
-	filePath := "/home/nexus/pipo.txt"
+	filePath = "/home/nexus/pipo.txt"
 	_, err := q.sock.Write([]byte(`{"execute":"guest-file-open", "arguments":{"path":"`+filePath+`","mode":"w+"}}`))
 	buf := make([]byte, 128)
 	_, err = q.sock.Read(buf)
@@ -51,7 +52,10 @@ func (q *QGACon)WriteFile(filePath string) error {
 	// content must be encoded in base64
 	content := "Hello ma poule!"
 	contentB64 := base64.StdEncoding.EncodeToString([]byte(content))
-	status, err = q.sock.Write([]byte(`{"execute":"guest-file-write", "arguments":{"handle":1000,"buf-b64":"`+contentB64+`"}}`))
+	status, err := q.sock.Write([]byte(`{"execute":"guest-file-write", "arguments":{"handle":1000,"buf-b64":"`+contentB64+`"}}`))
 	status, err = q.sock.Write([]byte(`{"execute":"guest-file-close", "arguments":{"handle":1000}}`))
+	if status < 0 {
+		return errors.New("write error")
+	}
 	return err
 }

src/vms/vms.go

@@ -2,7 +2,6 @@ package vms
 
 import (
 	"os"
-	"math"
 	"sort"
 	"sync"
 	"errors"
@@ -24,7 +23,6 @@ type (
 		dir string             // Base directory where VMs are stored
 		rwlock *sync.RWMutex   // RWlock to ensure the coherency of the map (m) of VMs
 		usedPorts [65536]bool  // Indicates which ports are used by the VMs
-		usedRAM int            // Used RAM by running VMs (in MB)
 	}
 )
 
@@ -41,7 +39,7 @@ func GetVMsInstance() *VMs {
 // NOTE: path is the root directory where VMs reside.
 func InitVMs() error {
 	vmsDir := paths.GetInstance().VMsDir
-	vms = &VMs { m: make(map[string]VM), dir: vmsDir, rwlock: new(sync.RWMutex), usedRAM: 0 }
+	vms = &VMs { m: make(map[string]VM), dir: vmsDir, rwlock: new(sync.RWMutex) }
 
 	errMsg := "Failed reading VMs directory: "
 	dirs1, err := utils.GetSubDirs(vmsDir)
@@ -172,18 +170,18 @@ func (vms *VMs)StartVM(vmID uuid.UUID) (int, string, error) {
 		return 0, "", err
 	}
 
-	// Check there will be at least 2GB of RAM left after the VM has started,
-	// otherwise, we prevent the execution of the VM to avoid RAM saturation.
-	// Furthermore, given Linux's KSVM technology allows page sharing, we
-	// assume it's able to save 30% of RAM (should be a conservative estimate).
 	_, availRAM, err := utils.GetRAM()
 	if err != nil {
 		return -1, "", errors.New("Failed obtaining memory info: "+err.Error())
 	}
 
-	vms.usedRAM += vm.Ram
-	if availRAM - int(math.Round(float64(vms.usedRAM)*0.7)) < 2048 {
-		vms.usedRAM -= vm.Ram
+	// Check there will be at least 16GB of RAM left after the VM has started,
+	// otherwise, we prevent the execution of the VM to avoid RAM saturation.
+	// Thanks to Linux's KSVM technology, pages sharing the same content are actually shared
+	// which dramatically reduces the amount of RAM being used (roughly ~50% in average).
+	log.Info("vm.RAM: ", vm.Ram)
+	log.Info("Available RAM: ", availRAM)
+	if availRAM - vm.Ram < 16*1024  {
 		return -1, "", errors.New("Insufficient free RAM to start VM")
 	}
 
@@ -207,7 +205,6 @@ func (vms *VMs)StartVM(vmID uuid.UUID) (int, string, error) {
 		vm.mutex.Unlock()
 		vms.rwlock.Lock()
 		vms.usedPorts[vm.Run.Port] = false
-		vms.usedRAM -= vm.Ram
 		vms.updateVMMap(vm)
 		vms.rwlock.Unlock()
 	}