CPU L2缓存初探

探索目的

为了设计高性能的内存数据库，往往要考虑CPU缓存的命中率，查阅资料发现，Intel架构的处理器有3级缓存的设置，其中L1，L2较小，L3较大但被三个核心所公用。在我使用的i7 4712mq中，使用dmidecode查看缓存大小：

inszva@inszva-Aspire-E5-572G:~$ sudo dmidecode
[sudo] password for inszva: 
# dmidecode 2.12
SMBIOS 2.8 present.
28 structures occupying 1951 bytes.
Table at 0x000E6F30.

Handle 0x0000, DMI type 0, 24 bytes
BIOS Information
    Vendor: Insyde Corp.
    Version: V1.05
    Release Date: 03/17/2015
    Address: 0xE0000
    Runtime Size: 128 kB
    ROM Size: 6144 kB
    Characteristics:
        PCI is supported
        BIOS is upgradeable
        BIOS shadowing is allowed
        Boot from CD is supported
        Selectable boot is supported
        EDD is supported
        Japanese floppy for NEC 9800 1.2 MB is supported (int 13h)
        Japanese floppy for Toshiba 1.2 MB is supported (int 13h)
        5.25"/360 kB floppy services are supported (int 13h)
        5.25"/1.2 MB floppy services are supported (int 13h)
        3.5"/720 kB floppy services are supported (int 13h)
        3.5"/2.88 MB floppy services are supported (int 13h)
        8042 keyboard services are supported (int 9h)
        CGA/mono video services are supported (int 10h)
        ACPI is supported
        USB legacy is supported
        BIOS boot specification is supported
        Targeted content distribution is supported
        UEFI is supported
    BIOS Revision: 1.5
    Firmware Revision: 1.5

Handle 0x0001, DMI type 1, 27 bytes
System Information
    Manufacturer: Acer
    Product Name: Aspire E5-572G
    Version: V1.05
    Serial Number: NXMV2CN01252001C033400
    UUID: F54CECF0-8EF4-E411-85C7-F0761CC0B25C
    Wake-up Type: Power Switch
    SKU Number: Aspire E5-572G_0922_V1.05
    Family: SharkBay System

Handle 0x0002, DMI type 2, 16 bytes
Base Board Information
    Manufacturer: Acer
    Product Name: EA50_HWS  
    Version: V1.05
    Serial Number: NBMV211001520310DC3400
    Asset Tag: Type2 - Board Asset Tag
    Features:
        Board is a hosting board
        Board is replaceable
    Location In Chassis: Type2 - Board Chassis Location
    Chassis Handle: 0x0003
    Type: Motherboard
    Contained Object Handles: 0

Handle 0x0003, DMI type 3, 23 bytes
Chassis Information
    Manufacturer: Acer
    Type: Notebook
    Lock: Not Present
    Version: Chassis Version
    Serial Number: Chassis Serial Number
    Asset Tag: Chassis Asset Tag
    Boot-up State: Safe
    Power Supply State: Safe
    Thermal State: Safe
    Security Status: None
    OEM Information: 0x00000000
    Height: Unspecified
    Number Of Power Cords: 1
    Contained Elements: 0
    SKU Number: Not Specified

Handle 0x0004, DMI type 4, 42 bytes
Processor Information
    Socket Designation: U3E1
    Type: Central Processor
    Family: Core i7
    Manufacturer: Intel(R) Corporation
    ID: C3 06 03 00 FF FB EB BF
    Signature: Type 0, Family 6, Model 60, Stepping 3
    Flags:
        FPU (Floating-point unit on-chip)
        VME (Virtual mode extension)
        DE (Debugging extension)
        PSE (Page size extension)
        TSC (Time stamp counter)
        MSR (Model specific registers)
        PAE (Physical address extension)
        MCE (Machine check exception)
        CX8 (CMPXCHG8 instruction supported)
        APIC (On-chip APIC hardware supported)
        SEP (Fast system call)
        MTRR (Memory type range registers)
        PGE (Page global enable)
        MCA (Machine check architecture)
        CMOV (Conditional move instruction supported)
        PAT (Page attribute table)
        PSE-36 (36-bit page size extension)
        CLFSH (CLFLUSH instruction supported)
        DS (Debug store)
        ACPI (ACPI supported)
        MMX (MMX technology supported)
        FXSR (FXSAVE and FXSTOR instructions supported)
        SSE (Streaming SIMD extensions)
        SSE2 (Streaming SIMD extensions 2)
        SS (Self-snoop)
        HTT (Multi-threading)
        TM (Thermal monitor supported)
        PBE (Pending break enabled)
    Version: Intel(R) Core(TM) i7-4712MQ CPU @ 2.30GHz
    Voltage: 0.9 V
    External Clock: 100 MHz
    Max Speed: 2300 MHz
    Current Speed: 2900 MHz
    Status: Populated, Enabled
    Upgrade: <OUT OF SPEC>
    L1 Cache Handle: 0x0006
    L2 Cache Handle: 0x0007
    L3 Cache Handle: 0x0008
    Serial Number: To Be Filled By O.E.M.
    Asset Tag: To Be Filled By O.E.M.
    Part Number: To Be Filled By O.E.M.
    Core Count: 4
    Core Enabled: 4
    Thread Count: 8
    Characteristics:
        64-bit capable
        Multi-Core
        Hardware Thread
        Execute Protection
        Enhanced Virtualization
        Power/Performance Control

Handle 0x0005, DMI type 7, 19 bytes
Cache Information
    Socket Designation: L1 Cache
    Configuration: Enabled, Not Socketed, Level 1
    Operational Mode: Write Back
    Location: Internal
    Installed Size: 32 kB
    Maximum Size: 32 kB
    Supported SRAM Types:
        Synchronous
    Installed SRAM Type: Synchronous
    Speed: Unknown
    Error Correction Type: Single-