2013/4/23 Ren Zhen <darwin.xupt@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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