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Implement basic TSC calibration

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This commit is contained in:
Ivan Chikish 2023-07-15 10:15:32 +03:00
parent 50a6d1a074
commit 4e37240cb9
3 changed files with 51 additions and 2 deletions
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4
orbis-kernel/include/orbis/KernelContext.hpp
View File

@ -51,6 +51,8 @@ public:
void deleteProcess(Process *proc);
Process *findProcessById(pid_t pid) const;
long getTscFreq();
void *kalloc(std::size_t size,
std::size_t align = __STDCPP_DEFAULT_NEW_ALIGNMENT__);
void kfree(void *ptr, std::size_t size);
@ -113,6 +115,8 @@ private:
UmtxChain m_umtx_chains[2][c_umtx_chains]{};
std::atomic<long> m_tsc_freq{0};
mutable shared_mutex m_proc_mtx;
utils::LinkedNode<Process> *m_processes = nullptr;
utils::kmap<utils::kstring, Ref<EventFlag>> m_event_flags;

46
orbis-kernel/src/KernelContext.cpp
View File

@ -24,7 +24,8 @@ KernelContext::KernelContext() {
pthread_mutex_init(&m_heap_mtx, &mtx_attr);
pthread_mutexattr_destroy(&mtx_attr);
std::printf("orbis::KernelContext initialized, addr=%p", this);
std::printf("orbis::KernelContext initialized, addr=%p\n", this);
std::printf("TSC frequency: %lu\n", getTscFreq());
}
KernelContext::~KernelContext() {}
@ -73,6 +74,49 @@ Process *KernelContext::findProcessById(pid_t pid) const {
return nullptr;
}
long KernelContext::getTscFreq() {
auto cal_tsc = []() -> long {
const long timer_freq = 1'000'000'000;
// Calibrate TSC
constexpr int samples = 40;
long rdtsc_data[samples];
long timer_data[samples];
long error_data[samples];
struct timespec ts0;
clock_gettime(CLOCK_MONOTONIC, &ts0);
long sec_base = ts0.tv_sec;
for (int i = 0; i < samples; i++) {
usleep(200);
error_data[i] = (__builtin_ia32_lfence(), __builtin_ia32_rdtsc());
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
rdtsc_data[i] = (__builtin_ia32_lfence(), __builtin_ia32_rdtsc());
timer_data[i] = ts.tv_nsec + (ts.tv_sec - sec_base) * 1'000'000'000;
}
// Compute average TSC
long acc = 0;
for (int i = 0; i < samples - 1; i++) {
acc += (rdtsc_data[i + 1] - rdtsc_data[i]) * timer_freq /
(timer_data[i + 1] - timer_data[i]);
}
// Rounding
acc /= (samples - 1);
constexpr long grain = 1'000'000;
return grain * (acc / grain + long{(acc % grain) > (grain / 2)});
};
long freq = m_tsc_freq.load();
if (freq)
return freq;
m_tsc_freq.compare_exchange_strong(freq, cal_tsc());
return m_tsc_freq.load();
}
void *KernelContext::kalloc(std::size_t size, std::size_t align) {
size = (size + (__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1)) &
~(__STDCPP_DEFAULT_NEW_ALIGNMENT__ - 1);

3
orbis-kernel/src/sys/sys_sysctl.cpp
View File

@ -1,3 +1,4 @@
#include "KernelContext.hpp"
#include "sys/sysproto.hpp"
orbis::SysResult orbis::sys___sysctl(Thread *thread, ptr<sint> name,
@ -232,7 +233,7 @@ orbis::SysResult orbis::sys___sysctl(Thread *thread, ptr<sint> name,
return ErrorCode::INVAL;
}
*(uint64_t *)old = 1000000000ull;
*(uint64_t *)old = g_context.getTscFreq();
return {};
default: