Re: Is there a way to obtain a machine's cache line size?

[Sad Clouds <cryintothebluesky%googlemail.com@localhost>]

On Thu, 20 Jan 2011 11:59:03 +0800
Dennis Ferguson <dennis.c.ferguson%gmail.com@localhost> wrote:

> Hello,
> 
> Is there a way to obtain the correct cache line size for the machine
> code is running on, both in the kernel and at user level?  I see
> there is a compile time constant CACHE_LINE_SIZE in <sys/param.h>
> which currently seems to be always be set to 64, but I'm pretty
> certain that is not necessarily a correct value.  For example, I'm
> pretty sure that for the PowerPC 32 and 128 are possibilities, and
> the same binary could run on machines with either line size so there
> is no correct compile-time answer.

You probably won't find many processors with cache lines greater than
64 bytes. If you're optimising for a particular processor, read
technical manuals to find out the size of cache lines, then simply
define CACHE_LINE_SIZE or whatever compile time constant you're using
to a different value.