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/* libjodycode: detect and report size of CPU caches on Linux
*
* Copyright (C) 2017-2026 by Jody Bruchon <jody@jodybruchon.com>
* Distributed under The MIT License
*
* If an error occurs or a cache is missing, zeroes are returned
* Unified caches populate l1/l2/l3; split caches populate lXi/lXd instead
*/
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "likely_unlikely.h"
#include "libjodycode.h"
/* For non-Linux systems, use a default dummy set of numbers.
* This opens up the possibility of future implementation on Windows and macOS. */
#ifndef __linux__
static const struct jc_proc_cacheinfo static_cacheinfo = {
.l1 = 0, .l1i = 0, .l1d = 0,
.l2 = 0, .l2i = 0, .l2d = 0,
.l3 = 0, .l3i = 0, .l3d = 0
};
struct jc_proc_cacheinfo *jc_get_proc_cacheinfo(int cleanup)
{
static struct jc_proc_cacheinfo *pci = NULL;
if (unlikely(cleanup != 0)) {
if (likely(pci != NULL)) free(pci);
return NULL;
}
pci = (struct jc_proc_cacheinfo *)calloc(1, sizeof(struct jc_proc_cacheinfo));
if (pci == NULL) return NULL;
memcpy(pci, &static_cacheinfo, sizeof(struct jc_proc_cacheinfo));
return pci;
}
#endif /* not __linux */
/* None of this code is useful outside of Linux */
#ifdef __linux__
static char *pathidx;
static char buf[16];
static char path[64] = "/sys/devices/system/cpu/cpu0/cache/index";
/*** End declarations, begin code ***/
/* Linux sysfs */
static size_t read_procfile(const char * const restrict name)
{
FILE *fp;
size_t i;
if (unlikely(name == NULL)) return 0;
memset(buf, 0, 16);
/* Create path */
*pathidx = '\0';
strcpy(pathidx, name);
fp = fopen(path, "rb");
if (fp == NULL) return 0;
i = fread(buf, 1, 16, fp);
if (ferror(fp)) return 0;
fclose(fp);
*(buf + 15) = '\0';
return i;
}
struct jc_proc_cacheinfo *jc_get_proc_cacheinfo(int cleanup)
{
static struct jc_proc_cacheinfo *pci = NULL;
char *idx;
size_t i;
size_t size;
int level;
char type;
char index;
if (unlikely(cleanup != 0)) {
if (likely(pci != NULL)) free(pci);
return NULL;
}
if (pci != NULL) return pci;
i = strlen(path);
if (i > 48) return NULL;
idx = path + i;
pathidx = idx + 1;
*pathidx = '/'; pathidx++;
pci = (struct jc_proc_cacheinfo *)calloc(1, sizeof(struct jc_proc_cacheinfo));
if (pci == NULL) return NULL;
for (index = '0'; index < '9'; index++) {
*idx = index;
/* Get the level for this index */
if (read_procfile("level") == 0) goto finish;
if (*buf < '1' || *buf > '3') goto error;
else level = (*buf) + 1 - '1';
/* Get the size */
if (read_procfile("size") == 0) goto error;
size = (size_t)atoi(buf) * 1024;
if (size == 0) goto error;
/* Get the type */
if (read_procfile("type") == 0) goto error;
if (*buf != 'U' && *buf != 'I' && *buf != 'D') goto error;
type = *buf;
/* Act on it */
switch (type) {
case 'D':
switch (level) {
case 1: pci->l1d = size; break;
case 2: pci->l2d = size; break;
case 3: pci->l3d = size; break;
default: goto error;
};
break;
case 'I':
switch (level) {
case 1: pci->l1i = size; break;
case 2: pci->l2i = size; break;
case 3: pci->l3i = size; break;
default: goto error;
};
break;
case 'U':
switch (level) {
case 1: pci->l1 = size; break;
case 2: pci->l2 = size; break;
case 3: pci->l3 = size; break;
default: goto error;
};
break;
default: break;
}
/* Continue to next index */
}
finish:
if (unlikely(pci->l1d == 0 && pci->l1i == 0 && pci->l1 == 0)) goto error;
return pci;
error:
if (pci != NULL) free(pci);
return NULL;
}
#endif /* __linux__ */
/* This is for testing only */
#ifdef JC_TEST
int main(void)
{
static struct jc_proc_cacheinfo pci;
jc_get_proc_cacheinfo(&pci);
printf("Cache info:\n\n");
printf("L1 I %4luK, D %4luK, U %4luK\n", pci.l1i >> 10, pci.l1d >> 10, pci.l1 >> 10);
printf("L2 I %4luK, D %4luK, U %4luK\n", pci.l2i >> 10, pci.l2d >> 10, pci.l2 >> 10);
if ((pci.l3d | pci.l3i | pci.l3) != 0) printf("L3 I %4luK, D %4luK, U %4luK\n", pci.l3i >> 10, pci.l3d >> 10, pci.l3 >> 10);
else printf("L3 does not exist\n");
return 0;
}
#endif
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