Utilização de toda a memória disponível

Olá pessoal. Sou iniciante no Linux - Manjaro XFCE.

Me parece que o sistema não esta utilizando toda a memória que tenho disponível (4gb)

Isto esta correto?

Se não, como devo proceder para que ele utilize os 4gb?

O comando free -ht esta retornando isto.

Captura de tela_2020-09-25_12-03-34

Informações do meu sistema

System:
  Kernel: 5.4.64-1-MANJARO x86_64 bits: 64 compiler: gcc v: 10.2.0 
  parameters: BOOT_IMAGE=/boot/vmlinuz-5.4-x86_64 
  root=UUID=0656753a-2c28-42e2-bcd0-0353336aa290 rw quiet udev.log_priority=3 
  Desktop: Xfce 4.14.2 tk: Gtk 3.24.20 info: xfce4-panel wm: xfwm4 
  dm: LightDM 1.30.0 Distro: Manjaro Linux 
Machine:
  Type: Laptop System: ASUSTeK product: N53Ta v: 1.0 serial: <filter> 
  Mobo: ASUSTeK model: N53Ta v: 1.0 serial: <filter> UEFI: American Megatrends 
  v: N53Ta.209 date: 12/10/2011 
Battery:
  ID-1: BAT0 charge: 41.1 Wh condition: 41.6/48.4 Wh (86%) volts: 12.5/11.1 
  model: ASUSTek M50--24 type: Li-ion serial: N/A status: Unknown 
  Device-1: hidpp_battery_0 model: Logitech Wireless Keyboard serial: <filter> 
  charge: 55% (should be ignored) rechargeable: yes status: Discharging 
CPU:
  Topology: Quad Core model: AMD A6-3420M APU with Radeon HD Graphics bits: 64 
  type: MCP arch: Fusion family: 12 (18) model-id: 1 stepping: N/A 
  microcode: 3000027 L2 cache: 4096 KiB 
  flags: lm nx pae sse sse2 sse3 sse4a svm bogomips: 11982 
  Speed: 801 MHz min/max: 800/1500 MHz boost: enabled Core speeds (MHz): 
  1: 799 2: 870 3: 801 4: 800 
  Vulnerabilities: Type: itlb_multihit status: Not affected 
  Type: l1tf status: Not affected 
  Type: mds status: Not affected 
  Type: meltdown status: Not affected 
  Type: spec_store_bypass status: Not affected 
  Type: spectre_v1 
  mitigation: usercopy/swapgs barriers and __user pointer sanitization 
  Type: spectre_v2 
  mitigation: Full AMD retpoline, STIBP: disabled, RSB filling 
  Type: srbds status: Not affected 
  Type: tsx_async_abort status: Not affected 
Graphics:
  Device-1: AMD Sumo [Radeon HD 6520G] vendor: ASUSTeK driver: radeon 
  v: kernel bus ID: 00:01.0 chip ID: 1002:9647 
  Device-2: AMD Whistler [Radeon HD 6630M/6650M/6750M/7670M/7690M] 
  vendor: ASUSTeK driver: radeon v: kernel bus ID: 01:00.0 chip ID: 1002:6741 
  Device-3: Alcor Micro ASUS USB2.0 WebCam type: USB driver: uvcvideo 
  bus ID: 4-2:2 chip ID: 058f:a004 
  Display: x11 server: X.Org 1.20.8 driver: ati,radeon unloaded: modesetting 
  alternate: fbdev,vesa display ID: :0.0 screens: 1 
  Screen-1: 0 s-res: 1366x768 s-dpi: 96 s-size: 361x203mm (14.2x8.0") 
  s-diag: 414mm (16.3") 
  Monitor-1: LVDS res: 1366x768 hz: 60 dpi: 101 size: 344x193mm (13.5x7.6") 
  diag: 394mm (15.5") 
  OpenGL: renderer: AMD SUMO (DRM 2.50.0 / 5.4.64-1-MANJARO LLVM 10.0.1) 
  v: 3.3 Mesa 20.1.7 compat-v: 3.1 direct render: Yes 
Audio:
  Device-1: AMD BeaverCreek HDMI Audio [Radeon HD 6500D and 6400G-6600G series] driver: snd_hda_intel v: kernel bus ID: 00:01.1 chip ID: 1002:1714 
  Device-2: AMD FCH Azalia vendor: ASUSTeK driver: snd_hda_intel v: kernel 
  bus ID: 00:14.2 chip ID: 1022:780d 
  Sound Server: ALSA v: k5.4.64-1-MANJARO 
Network:
  Device-1: Qualcomm Atheros AR9485 Wireless Network Adapter vendor: AzureWave 
  driver: ath9k v: kernel port: e000 bus ID: 02:00.0 chip ID: 168c:0032 
  IF: wlp2s0 state: up mac: <filter> 
  Device-2: Qualcomm Atheros AR8151 v2.0 Gigabit Ethernet vendor: ASUSTeK 
  driver: atl1c v: 1.0.1.1-NAPI port: d000 bus ID: 03:00.0 chip ID: 1969:1083 
  IF: enp3s0 state: down mac: <filter> 
Drives:
  Local Storage: total: 465.76 GiB used: 15.44 GiB (3.3%) 
  SMART Message: Required tool smartctl not installed. Check --recommends 
  ID-1: /dev/sda vendor: Seagate model: ST9500325AS size: 465.76 GiB 
  block size: physical: 512 B logical: 512 B speed: 3.0 Gb/s 
  rotation: 5400 rpm serial: <filter> rev: SDM1 scheme: GPT 
Partition:
  ID-1: / raw size: 465.46 GiB size: 457.16 GiB (98.22%) 
  used: 15.44 GiB (3.4%) fs: ext4 dev: /dev/sda2 
Swap:
  Alert: No Swap data was found. 
Sensors:
  System Temperatures: cpu: 6280.0 C mobo: N/A 
  Fan Speeds (RPM): N/A 
  GPU: device: radeon temp: 42 C device: radeon temp: 43 C 
Info:
  Processes: 174 Uptime: 37m Memory: 3.33 GiB used: 1.39 GiB (41.7%) 
  Init: systemd v: 246 Compilers: gcc: 10.2.0 Packages: pacman: 900 lib: 275 
  Shell: Bash v: 5.0.18 running in: xfce4-terminal inxi: 3.1.05 

É normal. No free -ht, subtrai-se automaticamente a memória reservada pela placa mãe, pelo núcleo do Linux e pelos drivers do Linux (incluindo aqui a placa integrada).