linux - Intel CPU Cache Policy

Question

I have a laptop with an Intel(R) Core(TM) i5-2450M CPU @ 2.50GHz processor. I'm on Ubuntu 12.04 (x86_64) and I'm trying to find some info about my processor.

I was able to find most of the information I was looking for using

cat /proc/cpuinfo

and

lscpu

What I want to also find out is the cache policy that is used on each cache level. Is it write back or write through?

Is there any tool that I can use to find out such info?

Thanks in advance.

Answer 1

This is not something you can query from CPUID or such, nor can you configure your CPU to do one or the other, thus there exists no tool for querying. What you can query is the cache associativity, the cache line size, and the cache size, for example via /proc/cpuinfo.

All Intel-compatible CPUs during the last one/two decades used a write-back strategy for caches (which presumes fetching a cache line first to allow partial writes). Of course that's the theory, reality is slighly more complex than that.

Virtually all processors (your model included) have one or several forms of write combining (or fill buffers as Intel calls it since Merom), and all but the most antique Intel-compatible CPUs support uncached writes from SSE registers (which again uses a form of write-combining). And then of course, there are things like on-chip cache coherence protocols and snoop filtering and other mechanisms to ensure cache coherency both between cores of one processor and between different processors in a multi-processor system.
Nevertheless -- the general cache policy is still write-back.