https://www.reddit.com/r/programming/comments/4jfoez/cache_sizes_with_cpuid_in_c_and_d/http://blog.melkerlitsgard.se/2016/05/12/cache-sizes-with-cpuid/
Example code from the article:
int getCacheSize(int cacheLevel)
{
// Intel stores it's cache information in eax4, with ecx as index
// The information received is as following:
// ebx[31:22] = Ways of associativity
// ebx[21:12] = Physical line partitions
// ebx[11: 0] = Line size
asm
{
mov EAX, functionID;
mov ECX, cacheLevl; // The index here is the cache level (0 = L1i, 1 = L1d, 2 = L2 etc.)
cpuid;
mov cpuInfo, EAX;
mov cpuInfo + 4, EBX;
mov cpuInfo + 8, ECX;
mov cpuInfo + 12, EDX;
}
int ways = cpuInfo[1] & 0xffc00000; // This receives bit 22 to 31 from the ebx register
ways >>= 22; // Bitshift it 22 bits to get the real value, since we started reading from bit 22
int partitions = cpuInfo[1] & 0x7fe00; // This receives bit 12 to 22
partitions >>= 12; // Same here, bitshift 12 bits
int lineSize = cpuInfo[1] & 0x7ff; // This receives bit 0 to 11
int sets = cpuInfo[2]; // The sets are the value of the ecx register
// All of these values needs one appended to them to get the real value
return (ways + 1) * (partitions + 1) * (lineSize + 1) * (sets + 1);
}
Comment #1 by ilyayaroshenko — 2016-07-08T14:04:53Z
This is compiles:
/++
Returns: cache size in KBs.
Params:
cacheLevel = cache level (0 = L1d, 1 = L1i, 2 = L2 etc.)
+/
int getCacheSize(int cacheLevel)
{
enum functionID = 0x04;
// Intel stores it's cache information in eax4, with ecx as index
// The information received is as following:
// ebx[31:22] = Ways of associativity
// ebx[21:12] = Physical line partitions
// ebx[11: 0] = Line size
int[4] cpuInfo;
asm
{
mov EAX, functionID;
mov ECX, cacheLevel;
cpuid;
mov cpuInfo + 0x0, EAX;
mov cpuInfo + 0x4, EBX;
mov cpuInfo + 0x8, ECX;
mov cpuInfo + 0xC, EDX;
}
int ways = cpuInfo[1] & 0xffc00000; // This receives bit 22 to 31 from the ebx register
ways >>= 22; // Bitshift it 22 bits to get the real value, since we started reading from bit 22
int partitions = cpuInfo[1] & 0x3ff800; // This receives bit 12 to 21
partitions >>= 12; // Same here, bitshift 12 bits
int lineSize = cpuInfo[1] & 0x7ff; // This receives bit 0 to 11
int sets = cpuInfo[2]; // The sets are the value of the ecx register
// All of these values needs one appended to them to get the real value
int ret = (ways + 1) * (partitions + 1) * (lineSize + 1) * (sets + 1);
assert(ret % 1024 == 0);
return ret >> 10;
}
Comment #2 by ilyayaroshenko — 2016-07-09T17:43:35Z