On Tue, Apr 23, 2013 at 12:17 PM, Ren Zhen <darwin.xupt@gmail.com> wrote:

Hi everybody, For /sys/devices/system/cpu/cpu0/cache/index0/coherency_line_size, I execute the cmd '#cat coherency_line_size',then it return '64'. My OS is Ubuntu 12.04, CPU is intel core i3. Here is my problem, what is coherency_line_size ? what is its usage? Any help will be appreciated!

Hello, According to [1] and [2], that would be the size of a cache line. So, in your case, a cache line can hold 64 bytes of data. As for the usage, when you allocate memory, your CPU aligns it to 8 or 16 bytes, depending on whether you have a 32-bit machine or a 64-bit machine. In you wish to take advantage of the cache, you should align your memory allocations to the cache size (64 in your case). The functions listed at [3] assist you in doing that. Hope this helps. [1] http://superuser.com/questions/405355/meaning-of-files-in-cpu-folder-of-linu... [2] http://jkukunas.blogspot.ro/2009/04/determining-cache-coherency-line-size.ht... [3] http://linux.die.net/man/3/valloc -- Silviu Popescu