/ sys/device /和dmidecode报告的不同CPU缓存大小

Question

我正试图在我的系统中获得不同缓存级别的大小.

我试过两种技巧.

a)使用/ sys/device中的信息.这是输出.

$ cat /sys/devices/system/cpu/cpu0/cache/index1/size
32K
$ cat /sys/devices/system/cpu/cpu0/cache/index2/size
256K
$ cat /sys/devices/system/cpu/cpu0/cache/index3/size
8192K

b)使用来自dmidecode的信息

$ sudo dmidecode -t cache
Cache Information
    Socket Designation: CPU Internal L1
    Configuration: Enabled, Not Socketed, Level 1
    Operational Mode: Write Through
    Location: Internal
    Installed Size: 256 KB
    Maximum Size: 256 KB
        < .... >
Cache Information
    Socket Designation: CPU Internal L2
    Configuration: Enabled, Not Socketed, Level 2
    Operational Mode: Write Through
    Location: Internal
    Installed Size: 1024 KB
    Maximum Size: 1024 KB
        < .... >
Cache Information
    Socket Designation: CPU Internal L3
    Configuration: Enabled, Not Socketed, Level 3
    Operational Mode: Write Back
    Location: Internal
    Installed Size: 8192 KB
    Maximum Size: 8192 KB
        < .... >

报告的L2和L3缓存大小不同.关于a)为何出现这种差异的任何想法？b)哪种方法给出正确的值？

其他相关信息:

$uname -a
Linux 3.0.0-14-generic #23somerville3-Ubuntu SMP Mon Dec 12 09:20:18 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

cat /proc/cpuinfo 
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 58
model name  : Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz
stepping    : 9
cpu MHz     : 2400.000
cache size  : 8192 KB
physical id : 0
siblings    : 8
core id     : 0
cpu cores   : 4
apicid      : 0
initial apicid  : 0
fpu     : yes
fpu_exception   : yes
cpuid level : 13
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 x2apic popcnt aes xsave avx f16c rdrand lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid fsgsbase smep erms
bogomips    : 6784.23
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:
< ... >

Answer 1

一些东西:

1. 你有一个四核CPU
2. 将index<n>在名称/sys/devices/system/cpu/cpu<n>/cache不对应于L1/L2/L3等,有一个.../index<n>/level文件,它会告诉你缓存的水平.
3. 您的L1缓存分为两个缓存(可能index0和index1),一个用于数据,一个用于指令(请参阅.../index<n>/type),每个核心.4核*2个半*32K匹配dmidecode报告的256K .
4. L2缓存按核心分割.4核*256K(自index2)= 1024K,匹配dmidecodes L2号.