Linux-Kernel
Ubuntu 18.04 不使用超過 32GB 的 RAM
我剛剛用另外 32GB 的 RAM 升級了我的 PC。BIOS 和
lshw都承認所有四個 16GB RAM 模組的存在，但兩者都沒有free，top並且htop看到實際記憶體。$ sudo lshw adam-potwor width: 64 bits capabilities: smbios-3.0 dmi-3.0 smp vsyscall32 configuration: boot=normal chassis=desktop family=To Be Filled By O.E.M. sku=To Be Filled By O.E.M. uuid=00020003-0004-0005-0006-000700080009 *-core description: Motherboard product: X399 Taichi vendor: ASRock physical id: 0 serial: M80-AA002300154 *-firmware description: BIOS vendor: American Megatrends Inc. physical id: 0 version: P1.50 date: 09/05/2017 size: 64KiB capacity: 15MiB capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb biosbootspecification uefi *-memory description: System Memory physical id: 10 slot: System board or motherboard size: 64GiB *-bank:0 description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2134 MHz (0.5 ns) product: F4-3000C16-16GISB vendor: Unknown physical id: 0 serial: 00000000 slot: DIMM 0 size: 16GiB width: 64 bits clock: 2134MHz (0.5ns) *-bank:1 description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2134 MHz (0.5 ns) product: F4-3000C16-16GISB vendor: Unknown physical id: 1 serial: 00000000 slot: DIMM 1 size: 16GiB width: 64 bits clock: 2134MHz (0.5ns) *-bank:2 description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2134 MHz (0.5 ns) product: F4-3000C16-16GISB vendor: Unknown physical id: 2 serial: 00000000 slot: DIMM 0 size: 16GiB width: 64 bits clock: 2134MHz (0.5ns) *-bank:3 description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2134 MHz (0.5 ns) product: F4-3000C16-16GISB vendor: Unknown physical id: 3 serial: 00000000 slot: DIMM 1 size: 16GiB width: 64 bits clock: 2134MHz (0.5ns) *-bank:4 description: [empty] product: Unknown vendor: Unknown physical id: 4 serial: Unknown slot: DIMM 0 *-bank:5 description: [empty] product: Unknown vendor: Unknown physical id: 5 serial: Unknown slot: DIMM 1 *-bank:6 description: [empty] product: Unknown vendor: Unknown physical id: 6 serial: Unknown slot: DIMM 0 *-bank:7 description: [empty] product: Unknown vendor: Unknown physical id: 7 serial: Unknown slot: DIMM 1 *-cache:0 description: L1 cache physical id: 12 slot: L1 - Cache size: 1536KiB capacity: 1536KiB clock: 1GHz (1.0ns) capabilities: pipeline-burst internal write-back unified configuration: level=1 *-cache:1 description: L2 cache physical id: 13 slot: L2 - Cache size: 8MiB capacity: 8MiB clock: 1GHz (1.0ns) capabilities: pipeline-burst internal write-back unified configuration: level=2 *-cache:2 description: L3 cache physical id: 14 slot: L3 - Cache size: 32MiB capacity: 32MiB clock: 1GHz (1.0ns) capabilities: pipeline-burst internal write-back unified configuration: level=3 *-cpu description: CPU product: AMD Ryzen Threadripper 1950X 16-Core Processor vendor: Advanced Micro Devices [AMD] physical id: 15 bus info: cpu@0 version: AMD Ryzen Threadripper 1950X 16-Core Processor serial: Unknown slot: SP3r2 size: 1888MHz capacity: 4200MHz width: 64 bits clock: 100MHz capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid amd_dcm aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb hw_pstate sme ssbd vmmcall fsgsbase bmi1 avx2 smep bmi2 rdseed adx smap clflushopt sha_ni xsaveopt xsavec xgetbv1 xsaves clzero irperf xsaveerptr arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif overflow_recov succor smca cpufreq configuration: cores=16 enabledcores=16 threads=32 $ free -h total used free shared buff/cache available Mem: 31G 1.8G 27G 18M 1.8G 29G Swap: 14G 0B 14G我使用附帶的 Ubuntu 18.04
$ uname -r 4.15.0-33-generic核心。我可以在 AskUbuntu 上發布這個問題，但我覺得這個問題與核心相關，而不是特定於 Ubuntu。我目前的 grub 啟動條目顯示為
menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-9c791297-4f61-471a-ac23-6228987c316e' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi insmod part_gpt insmod ext2 set root='hd0,gpt1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1 b0fddb5e-191e-4de0-b8bd-543c3e22a22a else search --no-floppy --fs-uuid --set=root b0fddb5e-191e-4de0-b8bd-543c3e22a22a fi linux /vmlinuz-4.15.0-33-generic root=UUID=9c791297-4f61-471a-ac23-6228987c316e ro rootflags=subvol=@ quiet splash $vt_handoff initrd /initrd.img-4.15.0-33-generic }我還安裝了 Windows (tm) 來診斷問題。而 Windows 10 64bit 也只能看到 32GB 的 RAM。它將另外 32GB 診斷為“硬體保留”，這強烈表明主機板韌體中存在錯誤。
我還確認，我的主機板具有最新的 BIOS 版本（截至 2018 年 9 月 7 日）
$ dmesg |grep Memory [ 0.000000] Memory: 32676352K/33432868K available (12300K kernel code, 2470K rwdata, 4244K rodata, 2408K init, 2416K bss, 756516K reserved, 0K cma-reserved) [ 0.132315] x86/mm: Memory block size: 128MB
該問題是由不正確的記憶體插槽配置引起的。將記憶體更換為 A2、B2、C2 和 D2 插槽後，正如 Mark Patrick 所描述的，解決了所有問題。
所以這個故事的精神是：當 Linux（或 Windows）沒有使用所有已安裝的記憶體時（即使它看到插槽中的晶片），請檢查記憶體模組是否插入正確的插槽中。