[HELP] Documentation on CPU:/sys/devices/system/cpu/cpuX/cache/indexX/shared_cpu_map

[edsionte]

2013/4/23 Ren Zhen <darwin.xupt at gmail.com>

> Hi all:
>     Can anybody help me to understand the usage of 'shared_cpu_map' in
> /sys/devices/system/cpu/cpuX/cache/indexX/.
>     when I execute the cmd--'#cat shared_cpu_map', it retures '05'.
>      And my computer use Ubuntu12.04,Intel core i3 CPU.
>      I have read one email in LKML,it says:
>
> "The patch also adds a bunch of interfaces under
> /sys/devices/system/cpu/cpuX/cache, showing various information about the
> caches.  Most useful field being shared_cpu_map, which says what caches are
> shared among which logical cpus. "
>
>      But I still cannot catch the meaning of  'which says what caches
> are shared among which logical cpus'.
>
 You should learn CPU TOPOLOGY firstly.
 and the number means which processors in system shared caches.

 index 0: level 1 data cache
 index 1: level 1 instruction cache
 index 2: level 2 cache
 index 3: level 3 cache

 usually, processors in a core( if Hyper-threading is turned on) share
level 1 and level2 caches.
 processors in a socket share level3 cache

>
>      Thanks.
> --
> Sincerely,
> Ren Zhen
>
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