On 2/13/21 11:17 PM, Charlie Gibbs wrote: > [This would probably be an FAQ if I knew the proper incantation...] > > I realized recently that a box I've been running for a while isn't > seeing all of its installed memory. The BIOS screens indicate that 8GB > is installed, but Debian (recently upgraded to Buster) only sees a bit > over 3GB. > > cjg@dragon:~$ head -1 /proc/meminfo > MemTotal: 3331096 kB > > During boot I noticed the following message: > > [ 0.012080] WARNING: BIOS bug: CPU MTRRs don't cover all of memory, > losing 4800MB of RAM. > > So I guess it's time to start learning about the wonderful world of MTRRs. > > cjg@dragon:~$ cat /proc/mtrr > reg00: base=0x000000000 ( 0MB), size= 2048MB, count=1: write-back > reg01: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back > reg02: base=0x0c0000000 ( 3072MB), size= 256MB, count=1: write-back > reg03: base=0x0cff00000 ( 3327MB), size= 1MB, count=1: uncachable > > cjg@dragon:~$ head -9 /proc/cpuinfo > processor : 0 > vendor_id : GenuineIntel > cpu family : 6 > model : 15 > model name : Intel(R) Core(TM)2 CPU 6300 @ 1.86GHz > stepping : 2 > microcode : 0x56 > cpu MHz : 1598.388 > cache size : 2048 KB > > Here's the first part of /var/log/messages: > > [ 0.000000] Linux version 4.19.0-6-amd64 > (debian-ker...@lists.debian.org) (gcc version 8.3.0 (Debian 8.3.0-6)) #1 > SMP Debian 4.19.67-2+deb10u1 (2019-09-20) > [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-4.19.0-6-amd64 > root=UUID=4d3143dd-d732-4755-b832-05753ab9c53a ro quiet > [ 0.000000] x86/fpu: x87 FPU will use FXSAVE > [ 0.000000] BIOS-provided physical RAM map: > [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000008efff] > usable > [ 0.000000] BIOS-e820: [mem 0x000000000008f000-0x000000000009ffff] > reserved > [ 0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] > reserved > [ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000cfd60fff] > usable > [ 0.000000] BIOS-e820: [mem 0x00000000cfd61000-0x00000000cfd6dfff] > reserved > [ 0.000000] BIOS-e820: [mem 0x00000000cfd6e000-0x00000000cfe1efff] > usable > [ 0.000000] BIOS-e820: [mem 0x00000000cfe1f000-0x00000000cfee8fff] > ACPI NVS > [ 0.000000] BIOS-e820: [mem 0x00000000cfee9000-0x00000000cfeecfff] > usable > [ 0.000000] BIOS-e820: [mem 0x00000000cfeed000-0x00000000cfef1fff] > ACPI data > [ 0.000000] BIOS-e820: [mem 0x00000000cfef2000-0x00000000cfef2fff] > usable > [ 0.000000] BIOS-e820: [mem 0x00000000cfef3000-0x00000000cfefefff] > ACPI data > [ 0.000000] BIOS-e820: [mem 0x00000000cfeff000-0x00000000cfefffff] > usable > [ 0.000000] BIOS-e820: [mem 0x00000000cff00000-0x00000000cfffffff] > reserved > [ 0.000000] BIOS-e820: [mem 0x00000000fff00000-0x00000000ffffffff] > reserved > [ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000022bffffff] > usable > [ 0.000000] NX (Execute Disable) protection: active > [ 0.000000] SMBIOS 2.4 present. > [ 0.000000] DMI: /DG965WH, BIOS MQ96510J.86A.1687.2007.0510.0258 > 05/10/2007 > [ 0.000000] tsc: Fast TSC calibration using PIT > [ 0.000000] tsc: Detected 1864.782 MHz processor > [ 0.011112] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved > [ 0.011115] e820: remove [mem 0x000a0000-0x000fffff] usable > [ 0.011126] last_pfn = 0x22c000 max_arch_pfn = 0x400000000 > [ 0.011134] MTRR default type: uncachable > [ 0.011135] MTRR fixed ranges enabled: > [ 0.011137] 00000-9FFFF write-back > [ 0.011139] A0000-FFFFF uncachable > [ 0.011140] MTRR variable ranges enabled: > [ 0.011142] 0 base 000000000 mask F80000000 write-back > [ 0.011144] 1 base 080000000 mask FC0000000 write-back > [ 0.011145] 2 base 0C0000000 mask FF0000000 write-back > [ 0.011147] 3 base 0CFF00000 mask FFFF00000 uncachable > [ 0.011148] 4 disabled > [ 0.011149] 5 disabled > [ 0.011149] 6 disabled > [ 0.011150] 7 disabled > [ 0.011968] x86/PAT: Configuration [0-7]: WB WC UC- UC WB WP UC- WT > [ 0.012074] e820: update [mem 0xcff00000-0x22bffffff] usable ==> > reserved > [ 0.012080] WARNING: BIOS bug: CPU MTRRs don't cover all of memory, > losing 4800MB of RAM. > > Is there some sort of HOWTO that covers this stuff? Where do I go from > here? >
Hi Charlie, try to update your system first. In your log kernel version is 4.19.67-2+deb10u1 (2019-09-20), latest in Buster is 4.19.171-2 (2021-01-30). I am not sure that this update will help you but I guess it won't become worse. Kind regards Georgi
