Re: [Valgrind-users] Warnings with cachegrind tool

[Nicholas N. <nj...@cs...>]

On Thu, 12 Oct 2006, Zhiyao Tu wrote:

> Hi,
>
> I planed to use cachegrind tool to profile the instruction and data
> cache usage in my program. When I startup it with default options
> "valgrind --tool=cachegrind MyProgram", it shows following information
> at the beginning:
>
> ......
> --11725-- warning: Unknown Intel cache config value (0xB1), ignoring
> --11725-- warning: Unknown Intel cache config value (0x5), ignoring
> --11725-- warning: Unknown Intel cache config value (0xF0), ignoring
> --11725-- warning: Unknown Intel cache config value (0x57), ignoring
> --11725-- warning: Unknown Intel cache config value (0x56), ignoring
> --11725-- warning: Unknown Intel cache config value (0x49), ignoring
> --11725-- warning: Unknown Intel cache config value (0xB4), ignoring
> --11725-- warning: L2 cache not installed, ignore L2 results.
> ......
>
> The valgrind I used is valgrind-3.2.0-Debian. Seems that it can't
> recognize the CPU cache config. Shall I specified the I1/D1/L2 options
> directly in command line?

Yes!

> If so, what values to use? According to the
> content of /proc/cpuinfo, my box has 4 CPUs, every one is like this:
>
> cache size      : 4096 KB

I think that's the L2 size.  As for the I1/D1, I don't know, you could try 
googling for it.

Ultimately due to various approximations Cachegrind's results are not exact 
-- you're unlikely to get them closely matching results from hardware 
counters, for example.  Instead, think of Cachegrind's results as giving you 
an idea of your program's cache behaviour in general, in which case it 
doesn't matter if the cache configuration doesn't match reality exactly.

Nick