/sys/device/和dmidecode报告的不同CPU缓存大小

问题描述

我正在尝试获取系统中不同缓存级别的大小.

I'm trying to get the size of different cache level in my system.

我尝试了两种技术.

a)使用/sys/device中的信息.这是输出.

a) Using information from /sys/device. Here is the output.

$ 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dmidecode中的信息

b) Using information from dmidecode

$ 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)为什么会有这种差异的任何想法? b)哪种方法给出正确的值?

The size reported for L2 and L3 cache is different. Any ideas as to a) why this discrepancy? b) Which method gives the correct value?

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:
< ... >

推荐答案

几件事:

1. 您有一个四核CPU
2. /sys/devices/system/cpu/cpu<n>/cache中的index<n>名称与L1/L2/L3等不对应.有一个.../index<n>/level文件将告诉您缓存的级别.
3. 每个核心的L1缓存分为两个缓存(可能是index0和index1)，一个缓存用于数据，一个缓存用于指令(请参见.../index<n>/type). 4个内核* 2个一半* 32K与dmidecode报告的256K匹配.
4. L2缓存按内核拆分. 4个内核* 256K(来自index2)= 1024K，与dmidecode的L2编号匹配.

1. You have a quad-core CPU
2. The index<n> name in /sys/devices/system/cpu/cpu<n>/cache does not correspond to L1/L2/L3 etc. There is a .../index<n>/level file that will tell you the level of the cache.
3. Your L1 cache is split into two caches (likely index0 and index1), one for data, and one for instructions (see .../index<n>/type), per core. 4 cores * 2 halves * 32K matches the 256K that dmidecode reports.
4. The L2 cache is split per-core. 4 cores * 256K (from index2) = 1024K, which matches dmidecodes L2 number.

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