4

I don't undestand why my Ubuntu 18.04 reports 11.8Gb instead of expected +/-32Gb.
I have 2 physical "pieces" of 16Gb RAM each on a Dell laptop Precision 7510.

OS is 64 bits:

enter image description here

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.1 LTS
Release:    18.04
Codename:   bionic

Ubuntu reports 11.8Gb, command htop reports 11.8Gb of max RAM.

enter image description here

We made some tests at work:

  • we updated the bios to latest from Dell v1.16.3. Nothing changed.
  • with other pieces of 2x8Gb RAM from another colleague laptop, OS still reports 11.8Gb. Nothing changed
  • with only one piece of my 16Gb (testing both of my memory pieces one at a time), OS reported ... 16Gb ! Like if problem occurs only when there are 2 pieces of RAM in it, 2x16, or 2x8
  • we booted on a bootable Linux usb key (usb key of a colleague, this was not an Ubuntu, I don't asked him OS), and the 32Gb were detected by this alternate Linux OS!
  • Edit 2019/01/27 : I booted on a bootable USB key with a Live Ubuntu 18.04, result is same, vanilla Ubuntu 18.04 reports 11.8Go.

In this question, a quote of a line from /var/log/kern.log about memory may indicate some memory is reserved for video.

In my /var/log/kern.log, sometime this line says about 12Gb, sometime 16Gb:

Jan 24 11:06:29 proust kernel: [    0.000000] Memory: 12027524K/12374028K available (12300K kernel code, 2472K rwdata, 4252K rodata, 2408K init, 2416K bss, 346504K reserved, 0K cma-reserved)
...
Jan 25 16:01:55 proust kernel: [    0.000000] Memory: 16182536K/16592532K available (12300K kernel code, 2472K rwdata, 4252K rodata, 2408K init, 2416K bss, 409996K reserved, 0K cma-reserved)

Are those 12027524K available corresponding to the 11.8Gb the OS reports?
ie, if I took a screenshot when it indicated 16182536K, would OS reported then 16Gb available instead of 11.8 ?

Some extracts of /var/log/kern.log which might be helpful or not.

Jan 22 10:28:11 proust kernel: [    7.518122] Adding 33192956k swap on /dev/nvme0n1p5.  Priority:-2 extents:1 across:33192956k SSFS
[...]
Jan 22 10:28:11 proust kernel: [    1.655250] [drm] Detected VRAM RAM=2048M, BAR=256M
Jan 22 10:28:11 proust kernel: [    1.655250] [drm] RAM width 128bits DDR
Jan 22 10:28:11 proust kernel: [    1.655422] [TTM] Zone  kernel: Available graphics memory: 6044034 kiB
Jan 22 10:28:11 proust kernel: [    1.655423] [TTM] Zone   dma32: Available graphics memory: 2097152 kiB
Jan 22 10:28:11 proust kernel: [    1.655423] [TTM] Initializing pool allocator
Jan 22 10:28:11 proust kernel: [    1.655444] [TTM] Initializing DMA pool allocator
Jan 22 10:28:11 proust kernel: [    1.655454] [drm] radeon: 2048M of VRAM memory ready
Jan 22 10:28:11 proust kernel: [    1.655454] [drm] radeon: 2048M of GTT memory ready.
[...]
Jan 22 10:28:11 proust kernel: [    1.844114] [drm] Memory usable by graphics device = 4096M

and also, some errors (I never checked this /var/log/kern.log file)

Jan 22 10:28:11 proust kernel: [    5.573929] EXT4-fs (nvme0n1p1): re-mounted. Opts: errors=remount-ro
...
Jan 22 10:28:11 proust kernel: [    6.040729] thermal thermal_zone10: failed to read out thermal zone (-61)
...
Jan 22 10:28:11 proust kernel: [   10.690615] vboxdrv: module verification failed: signature and/or required key missing - tainting kernel
...
Jan 22 10:28:16 proust kernel: [   15.304753] ACPI Error: [SPRT] Namespace lookup failure, AE_ALREADY_EXISTS (20170831/dswload2-346)
...
Jan 22 10:28:16 proust kernel: [   15.304764] ACPI Error: Method parse/execution failed \_GPE._E42, AE_ALREADY_EXISTS (20170831/psparse-550)
...
Jan 22 10:28:21 proust kernel: [   20.552778] xhci_hcd 0000:3c:00.0: Host halt failed, -19
Jan 22 10:28:21 proust kernel: [   20.552780] xhci_hcd 0000:3c:00.0: Host not accessible, reset failed.
...
Jan 22 10:30:10 proust kernel: [  129.221450] radeon 0000:01:00.0: failed VCE resume (-22).
...
Jan 22 10:30:11 proust kernel: [  130.876028] [drm:uvd_v1_0_ib_test [radeon]] *ERROR* radeon: fence wait timed out.
Jan 22 10:30:11 proust kernel: [  130.876086] [drm:radeon_ib_ring_tests [radeon]] *ERROR* radeon: failed testing IB on ring 5 (-110).
Jan 22 10:30:11 proust kernel: [  130.876107] radeon 0000:01:00.0: scheduling IB failed (-12).
Jan 22 10:30:11 proust kernel: [  130.876149] [drm:radeon_vce_get_create_msg [radeon]] *ERROR* radeon: failed to schedule ib (-12).
Jan 22 10:30:11 proust kernel: [  130.876190] [drm:radeon_vce_ib_test [radeon]] *ERROR* radeon: failed to get create msg (-12).
Jan 22 10:30:11 proust kernel: [  130.876230] [drm:radeon_ib_ring_tests [radeon]] *ERROR* radeon: failed testing IB on ring 6 (-12).
Jan 22 10:30:11 proust kernel: [  130.876245] radeon 0000:01:00.0: scheduling IB failed (-12).
Jan 22 10:30:11 proust kernel: [  130.876282] [drm:radeon_vce_get_create_msg [radeon]] *ERROR* radeon: failed to schedule ib (-12).
Jan 22 10:30:11 proust kernel: [  130.876318] [drm:radeon_vce_ib_test [radeon]] *ERROR* radeon: failed to get create msg (-12).
Jan 22 10:30:11 proust kernel: [  130.876355] [drm:radeon_ib_ring_tests [radeon]] *ERROR* radeon: failed testing IB on ring 7 (-12).
...
Jan 22 10:30:22 proust kernel: [  141.892295] ACPI Error: [SPRT] Namespace lookup failure, AE_ALREADY_EXISTS (20170831/dswload2-346)

I see also a lot of non error lines:

Jan 22 18:42:28 proust kernel: [29667.466039] [drm] Reducing the compressed framebuffer size. This may lead to less power savings than a non-reduced-size. Try to increase stolen memory size if available in BIOS.

Here are some commands found on other threads:

$ cat /proc/meminfo 
MemTotal:       12324368 kB
MemFree:          267520 kB
MemAvailable:    5806556 kB
Buffers:         1055348 kB
Cached:          5303968 kB
SwapCached:            0 kB
Active:          6774156 kB
Inactive:        4251464 kB
Active(anon):    4678200 kB
Inactive(anon):  1035304 kB
Active(file):    2095956 kB
Inactive(file):  3216160 kB
Unevictable:         112 kB
Mlocked:             112 kB
SwapTotal:      33192956 kB
SwapFree:       33192956 kB
Dirty:              4360 kB
Writeback:             0 kB
AnonPages:       4666392 kB
Mapped:           912788 kB
Shmem:           1047204 kB
Slab:             724556 kB
SReclaimable:     554796 kB
SUnreclaim:       169760 kB
KernelStack:       22000 kB
PageTables:       105136 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    39355140 kB
Committed_AS:   18975512 kB
VmallocTotal:   34359738367 kB
VmallocUsed:           0 kB
VmallocChunk:          0 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      466080 kB
DirectMap2M:    12146688 kB
DirectMap1G:     1048576 kB

$ free
              total        used        free      shared  buff/cache   available
Mem:       12324368     5342192     1503780     1142692     5478396     5511600
Swap:      33192956           0    33192956

And finally, result of command dmidecode (which I found here) which looks like it sees all the RAM (2 memory devices of 16384 MB each: Handle 0x0049 and Handle 0x004B and 2 available / empty slots Handle 0x004A and Handle 0x004BC):

$ sudo dmidecode
[...]
Handle 0x0048, DMI type 16, 23 bytes
Physical Memory Array
    Location: System Board Or Motherboard
    Use: System Memory
    Error Correction Type: None
    Maximum Capacity: 64 GB
    Error Information Handle: Not Provided
    Number Of Devices: 4

Handle 0x0049, DMI type 17, 40 bytes
Memory Device
    Array Handle: 0x0048
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 16384 MB
    Form Factor: SODIMM
    Set: None
    Locator: ChannelA-DIMM0
    Bank Locator: BANK 0
    Type: DDR4
    Type Detail: Synchronous
    Speed: 2133 MT/s
    Manufacturer: Micron
    Serial Number: 12161215
    Asset Tag: 2C0C0000
    Part Number: 16ATF2G64HZ-2G1A1   
    Rank: 2
    Configured Clock Speed: 2133 MT/s
    Minimum Voltage: Unknown
    Maximum Voltage: Unknown
    Configured Voltage: 1.2 V

Handle 0x004A, DMI type 17, 40 bytes
Memory Device
    Array Handle: 0x0048
    Error Information Handle: Not Provided
    Total Width: Unknown
    Data Width: Unknown
    Size: No Module Installed
    Form Factor: DIMM
    Set: None
    Locator: ChannelB-DIMM0
    Bank Locator: BANK 1
    Type: Unknown
    Type Detail: None
    Speed: Unknown
    Manufacturer: Not Specified
    Serial Number: Not Specified
    Asset Tag: Not Specified
    Part Number: Not Specified
    Rank: Unknown
    Configured Clock Speed: Unknown
    Minimum Voltage: Unknown
    Maximum Voltage: Unknown
    Configured Voltage: Unknown

Handle 0x004B, DMI type 17, 40 bytes
Memory Device
    Array Handle: 0x0048
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 16384 MB
    Form Factor: SODIMM
    Set: None
    Locator: ChannelB-DIMM1
    Bank Locator: BANK 2
    Type: DDR4
    Type Detail: Synchronous
    Speed: 2133 MT/s
    Manufacturer: Micron
    Serial Number: 12121212
    Asset Tag: 00000000
    Part Number: 16ATF2G64HZ-2G1A1   
    Rank: 2
    Configured Clock Speed: 2133 MT/s
    Minimum Voltage: Unknown
    Maximum Voltage: Unknown
    Configured Voltage: 1.2 V

Handle 0x004C, DMI type 17, 40 bytes
Memory Device
    Array Handle: 0x0048
    Error Information Handle: Not Provided
    Total Width: Unknown
    Data Width: Unknown
    Size: No Module Installed
    Form Factor: DIMM
    Set: None
    Locator: ChannelA-DIMM1
    Bank Locator: BANK 3
    Type: Unknown
    Type Detail: None
    Speed: Unknown
    Manufacturer: Not Specified
    Serial Number: Not Specified
    Asset Tag: Not Specified
    Part Number: Not Specified
    Rank: Unknown
    Configured Clock Speed: Unknown
    Minimum Voltage: Unknown
    Maximum Voltage: Unknown
    Configured Voltage: Unknown

Handle 0x004D, DMI type 19, 31 bytes
Memory Array Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x007FFFFFFFF
    Range Size: 32 GB
    Physical Array Handle: 0x0048
    Partition Width: 2

Any clue, explanation for my case, or information to verify is welcome.

Edit 2019-01-28

Result of memtest86 (default test, took about 7.5 hours)
It reports a FAIL with 25/48 tests passed (52%).
Could those error be responsible of Ubuntu not displaying 28/32Gb available, but other distrib like Fedora do?

enter image description here

Edit 2019-02-03

I booted on a Live Fedora 29 from a USB key.
Result looks the same, only 12Gb available for OS:

htop result on Fedora

htop fedora

Fedora OS details window

enter image description here

Result of dmesg | grep Memory:

[liveuser@localhost-live ~]$ dmesg | grep Memory
[    0.000000] Memory: 12264216K/12607208K available (12300K kernel code, 1624K rwdata, 4056K rodata, 2160K init, 1336K bss, 342992K reserved, 0K cma-reserved)
[    0.024277] x86/mm: Memory block size: 128MB
[    3.774268] usb 1-1: Product: USB Flash Memory
[    6.433239] scsi 5:0:0:0: Direct-Access              USB Flash Memory 5.00 PQ: 0 ANSI: 0 CCS

I also add the whole dmesg start on Fedora, until this "memory" line.
Is the block/section BIOS-provided physical RAM map normal?

[liveuser@localhost-live ~]$ dmesg 
[    0.000000] Linux version 4.18.16-300.fc29.x86_64 (mockbuild@bkernel04.phx2.fedoraproject.org) (gcc version 8.2.1 20180801 (Red Hat 8.2.1-2) (GCC)) #1 SMP Sat Oct 20 23:24:08 UTC 2018
[    0.000000] Command line: BOOT_IMAGE=vmlinuz initrd=initrd.img root=live:CDLABEL=Fedora-WS-Live-29-1-2 rd.live.image rd.live.check quiet
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x008: 'MPX bounds registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x010: 'MPX CSR'
[    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    0.000000] x86/fpu: xstate_offset[3]:  832, xstate_sizes[3]:   64
[    0.000000] x86/fpu: xstate_offset[4]:  896, xstate_sizes[4]:   64
[    0.000000] x86/fpu: Enabled xstate features 0x1f, context size is 960 bytes, using 'compacted' format.
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009dbff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009dc00-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x0000000066540fff] usable
[    0.000000] BIOS-e820: [mem 0x0000000066541000-0x0000000066541fff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x0000000066542000-0x000000006b7a2fff] reserved
[    0.000000] BIOS-e820: [mem 0x000000006b7a3000-0x000000006b7dffff] ACPI data
[    0.000000] BIOS-e820: [mem 0x000000006b7e0000-0x000000006be59fff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000006be5a000-0x000000006fffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000e0000000-0x00000000efffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fe000000-0x00000000fe010fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fec00000-0x00000000fec00fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000039b2dcfff] usable
[    0.000000] BIOS-e820: [mem 0x000000039b2dd000-0x000000088dffffff] reserved
[    0.000000] NX (Execute Disable) protection: active
[    0.000000] SMBIOS 3.0.0 present.
[    0.000000] DMI: Dell Inc. Precision 7510/0M1YNP, BIOS 1.16.3 09/12/2018
[    0.000000] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved
[    0.000000] e820: remove [mem 0x000a0000-0x000fffff] usable
[    0.000000] last_pfn = 0x39b2dd max_arch_pfn = 0x400000000
[    0.000000] MTRR default type: write-back
[    0.000000] MTRR fixed ranges enabled:
[    0.000000]   00000-9FFFF write-back
[    0.000000]   A0000-BFFFF uncachable
[    0.000000]   C0000-FFFFF write-protect
[    0.000000] MTRR variable ranges enabled:
[    0.000000]   0 base 0080000000 mask 7F80000000 uncachable
[    0.000000]   1 base 0070000000 mask 7FF0000000 uncachable
[    0.000000]   2 base 006E000000 mask 7FFE000000 uncachable
[    0.000000]   3 base 006D800000 mask 7FFF800000 uncachable
[    0.000000]   4 disabled
[    0.000000]   5 disabled
[    0.000000]   6 disabled
[    0.000000]   7 disabled
[    0.000000]   8 disabled
[    0.000000]   9 disabled
[    0.000000] x86/PAT: Configuration [0-7]: WB  WC  UC- UC  WB  WP  UC- WT  
[    0.000000] last_pfn = 0x66541 max_arch_pfn = 0x400000000
[    0.000000] found SMP MP-table at [mem 0x000fce40-0x000fce4f] mapped at [(____ptrval____)]
[    0.000000] Base memory trampoline at [(____ptrval____)] 97000 size 24576
[    0.000000] Using GB pages for direct mapping
[    0.000000] BRK [0x348aaf000, 0x348aaffff] PGTABLE
[    0.000000] BRK [0x348ab0000, 0x348ab0fff] PGTABLE
[    0.000000] BRK [0x348ab1000, 0x348ab1fff] PGTABLE
[    0.000000] BRK [0x348ab2000, 0x348ab2fff] PGTABLE
[    0.000000] BRK [0x348ab3000, 0x348ab3fff] PGTABLE
[    0.000000] BRK [0x348ab4000, 0x348ab4fff] PGTABLE
[    0.000000] BRK [0x348ab5000, 0x348ab5fff] PGTABLE
[    0.000000] BRK [0x348ab6000, 0x348ab6fff] PGTABLE
[    0.000000] RAMDISK: [mem 0x63526000-0x66540fff]
[    0.000000] ACPI: Early table checksum verification disabled
[    0.000000] ACPI: RSDP 0x00000000000E98B0 000024 (v02 DELL  )
[    0.000000] ACPI: XSDT 0x000000006B7AF0B0 0000DC (v01 DELL   CBX3     01072009 AMI  00010013)
[    0.000000] ACPI: FACP 0x000000006B7D0780 00010C (v05 DELL   CBX3     01072009 AMI  00010013)
[    0.000000] ACPI: DSDT 0x000000006B7AF218 021568 (v02 DELL   CBX3     01072009 INTL 20120913)
[    0.000000] ACPI: FACS 0x000000006BE57E80 000040
[    0.000000] ACPI: APIC 0x000000006B7D0890 0000BC (v03 DELL   CBX3     01072009 AMI  00010013)
[    0.000000] ACPI: FPDT 0x000000006B7D0950 000044 (v01 DELL   CBX3     01072009 AMI  00010013)
[    0.000000] ACPI: MCFG 0x000000006B7D0998 00003C (v01 DELL   CBX3     01072009 MSFT 00000097)
[    0.000000] ACPI: HPET 0x000000006B7D09D8 000038 (v01 DELL   CBX3     01072009 AMI. 0005000B)
[    0.000000] ACPI: SSDT 0x000000006B7D0A10 00046D (v01 SataRe SataTabl 00001000 INTL 20120913)
[    0.000000] ACPI: LPIT 0x000000006B7D0E80 000094 (v01 INTEL  SKL      00000000 MSFT 0000005F)
[    0.000000] ACPI: SSDT 0x000000006B7D0F18 000248 (v02 INTEL  sensrhub 00000000 INTL 20120913)
[    0.000000] ACPI: SSDT 0x000000006B7D1160 002BAE (v02 INTEL  PtidDevc 00001000 INTL 20120913)
[    0.000000] ACPI: SSDT 0x000000006B7D3D10 0007D9 (v02 INTEL  xh_rvp07 00000000 INTL 20120913)
[    0.000000] ACPI: DBGP 0x000000006B7D44F0 000034 (v01 INTEL           00000000 MSFT 0000005F)
[    0.000000] ACPI: DBG2 0x000000006B7D4528 000054 (v00 INTEL           00000000 MSFT 0000005F)
[    0.000000] ACPI: SSDT 0x000000006B7D4580 003866 (v02 SaSsdt SaSsdt   00003000 INTL 20120913)
[    0.000000] ACPI: UEFI 0x000000006B7D7DE8 000042 (v01                 00000000      00000000)
[    0.000000] ACPI: SSDT 0x000000006B7D7E30 000E73 (v02 CpuRef CpuSsdt  00003000 INTL 20120913)
[    0.000000] ACPI: SSDT 0x000000006B7D8CA8 00435D (v02 DptfTa DptfTabl 00001000 INTL 20120913)
[    0.000000] ACPI: MSDM 0x000000006B7DD008 000055 (v03 DELL   CBX3     06222004 AMI  00010013)
[    0.000000] ACPI: SLIC 0x000000006B7DD060 000176 (v03 DELL   CBX3     01072009 MSFT 00010013)
[    0.000000] ACPI: SSDT 0x000000006B7DD1D8 000094 (v02 SgRef  SgPeg    00001000 INTL 20120913)
[    0.000000] ACPI: DMAR 0x000000006B7DD270 0000A8 (v01 INTEL  SKL      00000001 INTL 00000001)
[    0.000000] ACPI: TPM2 0x000000006B7DD318 000034 (v03        Tpm2Tabl 00000001 AMI  00000000)
[    0.000000] ACPI: SSDT 0x000000006B7DD350 000F00 (v01 AmdRef AmdTabl  00001000 INTL 20120913)
[    0.000000] ACPI: ASF! 0x000000006B7DE250 0000A5 (v32 INTEL   HCG     00000001 TFSM 000F4240)
[    0.000000] ACPI: Local APIC address 0xfee00000
[    0.000000] No NUMA configuration found
[    0.000000] Faking a node at [mem 0x0000000000000000-0x000000039b2dcfff]
[    0.000000] NODE_DATA(0) allocated [mem 0x39b2b2000-0x39b2dcfff]
[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x0000000000001000-0x0000000000ffffff]
[    0.000000]   DMA32    [mem 0x0000000001000000-0x00000000ffffffff]
[    0.000000]   Normal   [mem 0x0000000100000000-0x000000039b2dcfff]
[    0.000000]   Device   empty
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000000001000-0x000000000009cfff]
[    0.000000]   node   0: [mem 0x0000000000100000-0x0000000066540fff]
[    0.000000]   node   0: [mem 0x0000000100000000-0x000000039b2dcfff]
[    0.000000] Reserved but unavailable: 26694 pages
[    0.000000] Initmem setup node 0 [mem 0x0000000000001000-0x000000039b2dcfff]
[    0.000000] On node 0 totalpages: 3151802
[    0.000000]   DMA zone: 64 pages used for memmap
[    0.000000]   DMA zone: 21 pages reserved
[    0.000000]   DMA zone: 3996 pages, LIFO batch:0
[    0.000000]   DMA32 zone: 6486 pages used for memmap
[    0.000000]   DMA32 zone: 415041 pages, LIFO batch:31
[    0.000000]   Normal zone: 42700 pages used for memmap
[    0.000000]   Normal zone: 2732765 pages, LIFO batch:31
[    0.000000] Reserving Intel graphics memory at [mem 0x6e000000-0x6fffffff]
[    0.000000] ACPI: PM-Timer IO Port: 0x1808
[    0.000000] ACPI: Local APIC address 0xfee00000
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x01] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x02] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x03] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x04] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x05] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x06] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x07] high edge lint[0x1])
[    0.000000] ACPI: LAPIC_NMI (acpi_id[0x08] high edge lint[0x1])
[    0.000000] IOAPIC[0]: apic_id 2, version 32, address 0xfec00000, GSI 0-119
[    0.000000] ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl)
[    0.000000] ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
[    0.000000] ACPI: IRQ0 used by override.
[    0.000000] ACPI: IRQ9 used by override.
[    0.000000] Using ACPI (MADT) for SMP configuration information
[    0.000000] ACPI: HPET id: 0x8086a701 base: 0xfed00000
[    0.000000] smpboot: Allowing 8 CPUs, 0 hotplug CPUs
[    0.000000] PM: Registered nosave memory: [mem 0x00000000-0x00000fff]
[    0.000000] PM: Registered nosave memory: [mem 0x0009d000-0x0009dfff]
[    0.000000] PM: Registered nosave memory: [mem 0x0009e000-0x0009ffff]
[    0.000000] PM: Registered nosave memory: [mem 0x000a0000-0x000dffff]
[    0.000000] PM: Registered nosave memory: [mem 0x000e0000-0x000fffff]
[    0.000000] PM: Registered nosave memory: [mem 0x66541000-0x66541fff]
[    0.000000] PM: Registered nosave memory: [mem 0x66542000-0x6b7a2fff]
[    0.000000] PM: Registered nosave memory: [mem 0x6b7a3000-0x6b7dffff]
[    0.000000] PM: Registered nosave memory: [mem 0x6b7e0000-0x6be59fff]
[    0.000000] PM: Registered nosave memory: [mem 0x6be5a000-0x6fffffff]
[    0.000000] PM: Registered nosave memory: [mem 0x70000000-0xdfffffff]
[    0.000000] PM: Registered nosave memory: [mem 0xe0000000-0xefffffff]
[    0.000000] PM: Registered nosave memory: [mem 0xf0000000-0xfdffffff]
[    0.000000] PM: Registered nosave memory: [mem 0xfe000000-0xfe010fff]
[    0.000000] PM: Registered nosave memory: [mem 0xfe011000-0xfebfffff]
[    0.000000] PM: Registered nosave memory: [mem 0xfec00000-0xfec00fff]
[    0.000000] PM: Registered nosave memory: [mem 0xfec01000-0xfedfffff]
[    0.000000] PM: Registered nosave memory: [mem 0xfee00000-0xfee00fff]
[    0.000000] PM: Registered nosave memory: [mem 0xfee01000-0xfeffffff]
[    0.000000] PM: Registered nosave memory: [mem 0xff000000-0xffffffff]
[    0.000000] [mem 0x70000000-0xdfffffff] available for PCI devices
[    0.000000] Booting paravirtualized kernel on bare hardware
[    0.000000] clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1910969940391419 ns
[    0.000000] random: get_random_bytes called from start_kernel+0x93/0x558 with crng_init=0
[    0.000000] setup_percpu: NR_CPUS:1024 nr_cpumask_bits:8 nr_cpu_ids:8 nr_node_ids:1
[    0.000000] percpu: Embedded 45 pages/cpu @(____ptrval____) s147456 r8192 d28672 u262144
[    0.000000] pcpu-alloc: s147456 r8192 d28672 u262144 alloc=1*2097152
[    0.000000] pcpu-alloc: [0] 0 1 2 3 4 5 6 7 
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 3102531
[    0.000000] Policy zone: Normal
[    0.000000] Kernel command line: BOOT_IMAGE=vmlinuz initrd=initrd.img root=live:CDLABEL=Fedora-WS-Live-29-1-2 rd.live.image rd.live.check quiet
[    0.000000] Memory: 12264216K/12607208K available (12300K kernel code, 1624K rwdata, 4056K rodata, 2160K init, 1336K bss, 342992K reserved, 0K cma-reserved)
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=8, Nodes=1
5
1

After changing the physical memory sticks, (replaced 2 old of 16Go per 4 of 8Go) I now have 31.2 Go detected.
Thus, it was a physical memory problem.

enter image description here

and also, with htop:

enter image description here

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