* Copyright 2023, Jérôme Duval, jerome.duval@gmail.com. All rights reserved.
* Distributed under the terms of the MIT License.
*/
#include <sched.h>
#include <syscalls.h>
#ifdef __x86_64__
#include <pthread.h>
#include <x86intrin.h>
#define IA32_FEATURE_RDPID (1 << 22) // RDPID Instruction
#define IA32_FEATURE_AMD_EXT_RDTSCP (1 << 27) // rdtscp instruction
typedef int (*sched_cpu_func)();
static pthread_once_t sSchedCpuInitOnce = PTHREAD_ONCE_INIT;
static sched_cpu_func sSchedCpuFunc = NULL;
static int
__sched_cpu_syscall()
{
return _kern_get_cpu();
}
static int
__sched_cpu_rdtscp()
{
uint32_t aux;
__rdtscp(&aux);
return aux;
}
static int
__sched_cpu_rdpid()
{
return _rdpid_u32();
}
static void
initSchedCpuFunc()
{
cpuid_info cpuInfo;
get_cpuid(&cpuInfo, 0, 0);
if (cpuInfo.eax_0.max_eax >= 0x7) {
get_cpuid(&cpuInfo, 0x7, 0);
if ((cpuInfo.regs.ecx & IA32_FEATURE_RDPID) != 0) {
sSchedCpuFunc = __sched_cpu_rdpid;
return;
}
}
get_cpuid(&cpuInfo, 0x80000000, 0);
if (cpuInfo.eax_0.max_eax >= 0x80000001) {
get_cpuid(&cpuInfo, 0x80000001, 0);
if ((cpuInfo.regs.edx & IA32_FEATURE_AMD_EXT_RDTSCP)!= 0) {
sSchedCpuFunc = __sched_cpu_rdtscp;
return;
}
}
sSchedCpuFunc = __sched_cpu_syscall;
}
int
sched_getcpu()
{
if (sSchedCpuFunc == NULL) {
pthread_once(&sSchedCpuInitOnce, &initSchedCpuFunc);
}
return sSchedCpuFunc();
}
#else
int
sched_getcpu()
{
return _kern_get_cpu();
}
#endif
