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VILLASnode/lib/tsc.c

77 lines
2.3 KiB
C

/** Measure time and sleep with IA-32 time-stamp counter.
*
* @file
* @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
* @copyright 2018, Institute for Automation of Complex Power Systems, EONERC
* @license GNU General Public License (version 3)
*
* VILLASnode
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*********************************************************************************/
#include <villas/tsc.h>
int tsc_init(struct tsc *t)
{
uint32_t eax, ebx, ecx, edx;
/** Check if TSC is supported */
__get_cpuid(0x1, &eax, &ebx, &ecx, &edx);
if (!(edx & bit_TSC))
return -2;
/** Check if RDTSCP instruction is supported */
__get_cpuid(0x80000001, &eax, &ebx, &ecx, &edx);
t->rdtscp_supported = edx & bit_RDTSCP;
/** Check if TSC is invariant */
__get_cpuid(0x80000007, &eax, &ebx, &ecx, &edx);
t->is_invariant = edx & bit_TSC_INVARIANT;
/** Intel SDM Vol 3, Section 18.7.3:
* Nominal TSC frequency = CPUID.15H.ECX[31:0] * CPUID.15H.EBX[31:0] ) ÷ CPUID.15H.EAX[31:0]
*/
__get_cpuid(0x15, &eax, &ebx, &ecx, &edx);
if (ecx != 0)
t->frequency = ecx * ebx / eax;
else {
int ret;
#ifdef __linux__
ret = kernel_get_cpu_frequency(&t->frequency);
if (ret)
return ret;
#elif defined(__APPLE__)
int64_t frequency;
size_t lenp = sizeof(frequency);
/** @todo: machdep.tsc.frequency seems to be a measured frequency (based on local APIC?
* We should figure out which frequency is more accurate */
// ret = sysctlbyname("hw.cpufrequency", &frequency, &lenp, NULL, 0);
ret = sysctlbyname("machdep.tsc.frequency", &frequency, &lenp, NULL, 0);
if (ret)
return ret;
t->frequency = frequency;
#endif
}
return 0;
}
uint64_t tsc_rate_to_cycles(struct tsc *t, double rate)
{
return t->frequency / rate;
}