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//+private
//+build linux
package time
import "core:intrinsics"
import "core:sys/unix"
_get_tsc_frequency :: proc "contextless" () -> (u64, bool) {
perf_attr := unix.Perf_Event_Attr{}
perf_attr.type = u32(unix.Perf_Type_Id.Hardware)
perf_attr.config = u64(unix.Perf_Hardware_Id.Instructions)
perf_attr.size = size_of(perf_attr)
perf_attr.flags = {.Disabled, .Exclude_Kernel, .Exclude_HV}
fd := unix.sys_perf_event_open(&perf_attr, 0, -1, -1, 0)
if fd == -1 {
return 0, false
}
defer unix.sys_close(fd)
page_size : uint = 4096
ret := unix.sys_mmap(nil, page_size, unix.PROT_READ, unix.MAP_SHARED, fd, 0)
if ret < 0 && ret > -4096 {
return 0, false
}
addr := rawptr(uintptr(ret))
defer unix.sys_munmap(addr, page_size)
event_page := (^unix.Perf_Event_mmap_Page)(addr)
if .User_Time not_in event_page.cap.flags {
return 0, false
}
frequency := u64((u128(1_000_000_000) << u128(event_page.time_shift)) / u128(event_page.time_mult))
return frequency, true
}
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