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Groups > linux.debian.user > #231710
| From | Charlie Gibbs <cgibbs@surfnaked.ca> |
|---|---|
| Newsgroups | linux.debian.user |
| Subject | Missing memory and the mystery of MTRRs |
| Date | 2021-02-13 22:50 +0100 |
| Message-ID | <BIaXE-1Mb-13@gated-at.bofh.it> (permalink) |
| Organization | linux.* mail to news gateway |
[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-kernel@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? -- cgibbs@surfnaked.ca (Charlie Gibbs)
Back to linux.debian.user | Previous | Next — Next in thread | Find similar | Unroll thread
Missing memory and the mystery of MTRRs Charlie Gibbs <cgibbs@surfnaked.ca> - 2021-02-13 22:50 +0100
Re: Missing memory and the mystery of MTRRs "Alexander V. Makartsev" <avbetev@gmail.com> - 2021-02-14 11:50 +0100
Re: Missing memory and the mystery of MTRRs Georgi Naplatanov <gosho@oles.biz> - 2021-02-14 20:50 +0100
Re: Missing memory and the mystery of MTRRs Charles Curley <charlescurley@charlescurley.com> - 2021-02-14 22:50 +0100
Re: Missing memory and the mystery of MTRRs Henrique de Moraes Holschuh <hmh@debian.org> - 2021-02-16 17:10 +0100
Re: Missing memory and the mystery of MTRRs Paul Duncan <paul.d@soi-team.org> - 2021-02-22 11:20 +0100
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