Good morning folks,
Yang Huang wrote:
Hi list,
finally I "steal" a piece of code from memtest86 3.2, named
cache_off(), invoke it in a module and insmod. I feel immediately the
system is slowed down!
Good work Yang! :-)
What is Memtest86 3.2 ?
I believe this will definitely disable the cache, though not yet sure
whether both L1 and L2 cache are disabled. Any suggestions?
here is the code below:
static inline void cache_off(void)
{
asm(
"push %eax\n\t"
"movl %cr0,%eax\n\t"
"orl $0x40000000,%eax\n\t" /* Set CD */
"movl %eax,%cr0\n\t"
"wbinvd\n\t"
"pop %eax\n\t");
}
What are we doing here ? I am not familiar with 'wbinvd' and 'cr0'
I googled up 'wbinvd'
Flushes internal cache, then signals the external cache to write
back current data followed by a signal to flush the external cache.
So this flushes both the Internal as well as External Cache. Now, here
is my question:
What do we mean by 'write back current data' ? where does the External
Cache write it back ? How does writing back help ?
Manav
have fun with it...
Yang
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