From 7d713866c5912646cd7eebbfa423673a2670e1ac Mon Sep 17 00:00:00 2001
From: Florent Gluck <florent.gluck@hesge.ch>
Date: Wed, 7 Sep 2022 16:49:42 +0200
Subject: [PATCH] Takes into account real RAM usage when estimating how much
RAM is left. This is used when a VM is stated in order to know whether there
is enough RAM left. We assume that KSM allows us to save ~30% or RAM.
---
src/utils/memory.go | 56 ++++++++++++++++++++++++++++++++++++++++-----
src/vms/vms.go | 20 ++++++++--------
2 files changed, 60 insertions(+), 16 deletions(-)
diff --git a/src/utils/memory.go b/src/utils/memory.go
index 1a6e9ab..a75f0b2 100644
--- a/src/utils/memory.go
+++ b/src/utils/memory.go
@@ -1,17 +1,59 @@
package utils
import (
- "syscall"
+ "os"
+ "bufio"
+ "strconv"
+ "strings"
)
-var totalRAM int
+// This function returns info about the system's RAM
+// by reading /proc/meminfo.
+// Beware: it is Linux SPECIFIC!
+// Returns total and avaiable memory in MB.
+func GetRAM() (int, int, error) {
+ f, err := os.Open("/proc/meminfo")
+ if err != nil {
+ return 0, 0, err
+ }
+ defer f.Close()
-// Returns: total RAM, shared RAM, free RAM and possibly an error.
+ scan := bufio.NewScanner(f)
+ scan.Split(bufio.ScanLines)
+
+ var memTotal int = -1
+ var memAvail int = -1
+
+ const units = 1024
+
+ for scan.Scan() {
+ s := scan.Text()
+ fields := strings.Split(s, ":")
+ attr := fields[0]
+ vals := strings.Split(strings.TrimSpace(fields[1]), " ")
+ val := strings.TrimSpace(vals[0])
+ attr = strings.TrimSpace(strings.ToLower(attr))
+ switch attr {
+ case "memtotal":
+ memTotal, _ = strconv.Atoi(val)
+ memTotal = memTotal/units
+ case "memavailable":
+ memAvail, _ = strconv.Atoi(val)
+ memAvail = memAvail/units
+ }
+ }
+
+ return memTotal, memAvail, nil
+}
+
+/*
+// This function is not used because it DOES NOT return the available RAM!
+// Returns: total RAM, shared RAM, buffered RAM, free RAM and possibly an error.
// RAM amounts are given in megabytes (MB).
-func GetRAM() (int, int, int, error) {
+func GetRAM() (int, int, int, int, error) {
in := &syscall.Sysinfo_t{}
if err := syscall.Sysinfo(in); err != nil {
- return 0, 0, 0, err
+ return 0, 0, 0, 0, err
}
const MB = 1024*1024
@@ -19,6 +61,8 @@ func GetRAM() (int, int, int, error) {
// We always convert to uint64 to match signature.
totalRam := int(uint64(in.Totalram)*uint64(in.Unit)/MB)
sharedRam := int(uint64(in.Sharedram)*uint64(in.Unit)/MB)
+ bufferedRam := int(uint64(in.Bufferram)*uint64(in.Unit)/MB)
freeRam := int(uint64(in.Freeram)*uint64(in.Unit)/MB)
- return totalRam, sharedRam, freeRam, nil
+ return totalRam, sharedRam, bufferedRam, freeRam, nil
}
+*/
\ No newline at end of file
diff --git a/src/vms/vms.go b/src/vms/vms.go
index 0e5277e..3112bc5 100644
--- a/src/vms/vms.go
+++ b/src/vms/vms.go
@@ -2,6 +2,7 @@ package vms
import (
"os"
+ "math"
"sort"
"sync"
"errors"
@@ -29,7 +30,6 @@ type (
var log = logger.GetInstance()
var vms *VMs
-var totalRAM int
// Returns a VMs "singleton".
// IMPORTANT: the InitVMs function must have been previously called!
@@ -40,13 +40,6 @@ func GetVMsInstance() *VMs {
// Creates all VMs from their files on disk.
// NOTE: path is the root directory where VMs reside.
func InitVMs() error {
- // Retrieves the total amount of RAM (in MB).
- ram, _, _, err := utils.GetRAM()
- if err != nil {
- return errors.New("Failed obtaining memory info: "+err.Error())
- }
- totalRAM = ram
-
vmsDir := paths.GetInstance().VMsDir
vms = &VMs { m: make(map[string]VM), dir: vmsDir, rwlock: new(sync.RWMutex), usedRAM: 0 }
@@ -179,10 +172,17 @@ func (vms *VMs)StartVM(vmID uuid.UUID) (int, string, error) {
return 0, "", err
}
- // Check there will be at least 1GB of RAM left after the VM has started,
+ // 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 totalRAM - vms.usedRAM < 1024 {
+ if availRAM - int(math.Round(float64(vms.usedRAM)*0.7)) < 2048 {
vms.usedRAM -= vm.Ram
return -1, "", errors.New("Insufficient free RAM to start VM")
}
--
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