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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/bitops.h>
#include "api/fs/fs.h"
#include "smt.h"
/**
* hweight_str - Returns the number of bits set in str. Stops at first non-hex
* or ',' character.
*/
static int hweight_str(char *str)
{
int result = 0;
while (*str) {
switch (*str++) {
case '0':
case ',':
break;
case '1':
case '2':
case '4':
case '8':
result++;
break;
case '3':
case '5':
case '6':
case '9':
case 'a':
case 'A':
case 'c':
case 'C':
result += 2;
break;
case '7':
case 'b':
case 'B':
case 'd':
case 'D':
case 'e':
case 'E':
result += 3;
break;
case 'f':
case 'F':
result += 4;
break;
default:
goto done;
}
}
done:
return result;
}
int smt_on(void)
{
static bool cached;
static int cached_result;
int cpu;
int ncpu;
if (cached)
return cached_result;
if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0) {
cached = true;
return cached_result;
}
cached_result = 0;
ncpu = sysconf(_SC_NPROCESSORS_CONF);
for (cpu = 0; cpu < ncpu; cpu++) {
unsigned long long siblings;
char *str;
size_t strlen;
char fn[256];
snprintf(fn, sizeof fn,
"devices/system/cpu/cpu%d/topology/thread_siblings", cpu);
if (sysfs__read_str(fn, &str, &strlen) < 0) {
snprintf(fn, sizeof fn,
"devices/system/cpu/cpu%d/topology/core_cpus", cpu);
if (sysfs__read_str(fn, &str, &strlen) < 0)
continue;
}
/* Entry is hex, but does not have 0x, so need custom parser */
siblings = hweight_str(str);
free(str);
if (siblings > 1) {
cached_result = 1;
break;
}
}
cached = true;
return cached_result;
}
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