linux – ‘free’和’/ proc / meminfo /报告总内存少于’dmide

发布时间：2020-12-13 16:44:10 所属栏目：Linux 来源：网络整理

导读：我们在托管中心(真实物理服务器,而不是VM)中有一台服务器,运行64位Debian(uname -r：3.16.0-4-amd64). / proc / meminforeports大约4 GiB总内存： $head -n 1 /proc/meminfoMemTotal: 4051692 kB 免费报告相同(我只查看总列;我不是在讨论使用,免费,共享,缓冲

我们在托管中心(真实物理服务器,而不是VM)中有一台服务器,运行64位Debian(uname -r：3.16.0-4-amd64).

/ proc / meminforeports大约4 GiB总内存：

$head -n 1 /proc/meminfo
MemTotal:        4051692 kB

免费报告相同(我只查看总列;我不是在讨论使用,免费,共享,缓冲,缓存)：

$free -k
             total       used       free     shared    buffers     cached
Mem:       4051692    3867356     184336     220908      63948    1203596
-/+ buffers/cache:    2599812    1451880
Swap:     15728208     652540   15075668

dmesg也是如此grep记忆：

$dmesg | grep Memory
[    0.000000] Memory: 4034240K/4185236K available (5287K kernel code,949K rwdata,1836K rodata,1208K init,840K bss,150996K reserved)

但dmidecode报告4 * 2 GiB = 8 GiB的RAM,如果我理解正确：

$sudo dmidecode --type memory

# dmidecode 2.12
SMBIOS 2.6 present.

Handle 0x0008,DMI type 5,24 bytes
Memory Controller Information
    Error Detecting Method: 64-bit ECC
    Error Correcting Capabilities:
        Single-bit Error Correcting
    Supported Interleave: One-way Interleave
    Current Interleave: One-way Interleave
    Maximum Memory Module Size: 4096 MB
    Maximum Total Memory Size: 16384 MB
    Supported Speeds:
        Other
    Supported Memory Types:
        DIMM
        SDRAM
    Memory Module Voltage: 3.3 V
    Associated Memory Slots: 4
        0x0009
        0x000A
        0x000B
        0x000C
    Enabled Error Correcting Capabilities:
        Single-bit Error Correcting

Handle 0x0009,DMI type 6,12 bytes
Memory Module Information
    Socket Designation: DIMM1A
    Bank Connections: 0 1
    Current Speed: Unknown
    Type: DIMM SDRAM
    Installed Size: 2048 MB (Single-bank Connection)
    Enabled Size: 2048 MB (Single-bank Connection)
    Error Status: OK

Handle 0x000A,12 bytes
Memory Module Information
    Socket Designation: DIMM1B
    Bank Connections: 2 3
    Current Speed: Unknown
    Type: DIMM SDRAM
    Installed Size: 2048 MB (Single-bank Connection)
    Enabled Size: 2048 MB (Single-bank Connection)
    Error Status: OK

Handle 0x000B,12 bytes
Memory Module Information
    Socket Designation: DIMM2A
    Bank Connections: 4 5
    Current Speed: Unknown
    Type: DIMM SDRAM
    Installed Size: 2048 MB (Single-bank Connection)
    Enabled Size: 2048 MB (Single-bank Connection)
    Error Status: OK

Handle 0x000C,12 bytes
Memory Module Information
    Socket Designation: DIMM2B
    Bank Connections: 6 7
    Current Speed: Unknown
    Type: DIMM SDRAM
    Installed Size: 2048 MB (Single-bank Connection)
    Enabled Size: 2048 MB (Single-bank Connection)
    Error Status: OK

Handle 0x002A,DMI type 16,15 bytes
Physical Memory Array
    Location: System Board Or Motherboard
    Use: System Memory
    Error Correction Type: Single-bit ECC
    Maximum Capacity: 16 GB
    Error Information Handle: Not Provided
    Number Of Devices: 4

Handle 0x002C,DMI type 17,28 bytes
Memory Device
    Array Handle: 0x002A
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 2048 MB
    Form Factor: DIMM
    Set: None
    Locator: DIMM1A
    Bank Locator: BANK0
    Type: DDR3
    Type Detail: Synchronous
    Speed: 1333 MHz
    Manufacturer: Micron        
    Serial Number: 501C6FDC
    Asset Tag: AssetTagNum0
    Part Number: 9JSF25672AZ-1G4D1 
    Rank: Unknown

Handle 0x002E,28 bytes
Memory Device
    Array Handle: 0x002A
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 2048 MB
    Form Factor: DIMM
    Set: None
    Locator: DIMM1B
    Bank Locator: BANK1
    Type: DDR3
    Type Detail: Synchronous
    Speed: 1333 MHz
    Manufacturer: Micron        
    Serial Number: 2A1C6FDC
    Asset Tag: AssetTagNum1
    Part Number: 9JSF25672AZ-1G4D1 
    Rank: Unknown

Handle 0x0030,28 bytes
Memory Device
    Array Handle: 0x002A
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 2048 MB
    Form Factor: DIMM
    Set: None
    Locator: DIMM2A
    Bank Locator: BANK2
    Type: DDR3
    Type Detail: Synchronous
    Speed: 1333 MHz
    Manufacturer: Micron        
    Serial Number: 511C6FDC
    Asset Tag: AssetTagNum2
    Part Number: 9JSF25672AZ-1G4D1 
    Rank: Unknown

Handle 0x0032,28 bytes
Memory Device
    Array Handle: 0x002A
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 2048 MB
    Form Factor: DIMM
    Set: None
    Locator: DIMM2B
    Bank Locator: BANK3
    Type: DDR3
    Type Detail: Synchronous
    Speed: 1333 MHz
    Manufacturer: Micron        
    Serial Number: 4B1C6FDC
    Asset Tag: AssetTagNum3
    Part Number: 9JSF25672AZ-1G4D1 
    Rank: Unknown

我错过了什么？
它是托管中心的服务器,所以不幸的是我无法轻易看到物理安装的内容.

编辑：
man dmidecode说：“通常情况下,DMI表中包含的信息不准确,不完整或完全错误.”也许dmidecode只是报告错误的数据？

编辑：
这不是Why is Linux reporting “free” memory strangely?的重复.那个问题是关于空闲内存,以及缓冲和缓存带来的混乱.我不关心空闲记忆,只关心总记忆.不要让我使用free命令欺骗你：我没有用它来查看可用内存量,只有总内存量.如果有人仍然认为这个问题是重复的,请解释我为什么,因为我不明白.

根据Lenniey的要求编辑：dmidecode -t1

$sudo dmidecode -t1
# dmidecode 2.12
SMBIOS 2.6 present.

Handle 0x0001,DMI type 1,27 bytes
System Information
        Manufacturer: Supermicro
        Product Name: X8SIL
        Version: 0123456789
        Serial Number: 0123456789
        UUID: 49434D53-0200-9037-2500-379025009946
        Wake-up Type: Power Switch
        SKU Number: To Be Filled By O.E.M.
        Family: To Be Filled By O.E.M.

解决方法

Supermicro X8SIL主板的手册可在以下位置获得：
http://www.supermicro.com/manuals/motherboard/3420/MNL-1130.pdf

在页32(也称为2-10),它表示如果使用Unbuffered(UDIMM)单列内存,使用1 GB DIMM和8 GB DIMM时支持的最大内存量将只有4 GB.

使用双列UDIMM,最大容量为16 GB.

只有使用Registered(RDIMM)四列内存模块才能达到32 GB的最大最大容量,并且使用它们时内存总线速度会受到影响.

关于“Micron 9JSF25672AZ-1G4D1”的一些谷歌搜索带我到这里：
https://www.compuram.biz/memory_module/mt9jsf25672az-1g4d1/micron.htm

似乎证实Micron Technology(MT)9JSF25672AZ-1G4D1确实是一款尺寸为2 GB的无缓冲单列内存模块.

在本手册的第34页(或2-13)中,它表示当仅使用4 GB的RAM时,将大量的RAM分配给系统设备,并且将无法使用.这可能至少考虑了一些安装了8 GB的丢失内存.遗憾的是,手册没有详细描述8 GB情况下的系统设备分配.

（编辑：李大同）

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