Access to the Timestamp Counter (of the current Core) More...

Enumerations
enum	Instruction { RDTSC , RDTSCP , CPUID_RDTSC , RDTSCP_CPUID , CR0_RDTSC }

Functions
uint32_t	ticks (bool use_pit=false)
	Gather the TSC frequency in ticks per milliseconds. More...

bool	available (Instruction instruction=RDTSC)
	Check availability of TSC. More...

uint64_t	nanoseconds (uint64_t delta)
	Convert a timestamp delta value to nanoseconds. More...

void	delay (uint64_t us)
	Actively wait the provided waiting time. More...

uint64_t	read (Instruction instruction=RDTSC)
	Reads the current timestamp counter. More...

Detailed Description

Access to the Timestamp Counter (of the current Core)

Enumerator
RDTSC	TSC Read with possible out-of-order execution.
RDTSCP	Pseudo serializing.
CPUID_RDTSC	Serializing (via CPUID) TSC read for begin of benchmark.
RDTSCP_CPUID	Serializing (via CPUID) TSC read for end of benchmark.
CR0_RDTSC	Serializing (via CR0) TSC read for end of benchmark if RDTSCP is not supported.

uint32_t TSC::ticks ( bool use_pit = false )

Gather the TSC frequency in ticks per milliseconds.

Parameters

use_pit Enforces the usage of the PIT if set, otherwise the processor infos are queried, at first.

Optional:: Implement calibration via PIT (in the local function ticksByPit()). For testing, it might be useful to compare the return values with different values of use_pit. The returned values should be similar 🙂

bool TSC::available ( Instruction instruction = RDTSC )

Check availability of TSC.

Parameters

instruction Test for the (unserialized) RDTSC or pseudo serializing RDTSCP instruction

uint64_t TSC::nanoseconds ( uint64_t delta )

Convert a timestamp delta value to nanoseconds.

Note: It is necessary to execute TSC::ticks() prior calling this function the first time, since it uses the cached TSC frequency value gathered by ticks() for the calculation.

Parameters

delta Delta between two timestamps

void TSC::delay ( uint64_t us )

Actively wait the provided waiting time.

Note: It is necessary to execute TSC::ticks() prior calling this function the first time, since it uses the cached TSC frequency value gathered by ticks() for the calculation.

Parameters

us	waiting time in microseconds

uint64_t TSC::read ( Instruction instruction = RDTSC )

inline

Reads the current timestamp counter.

While reading the timestamp counter is quite easy, it is difficult to prevent out-of-order execution.

See also: How to Benchmark Code Execution Times on Intel® IA-32 and IA-64 Instruction Set Architectures [benchmark_code_execution.pdf]

Parameters

instruction Instruction(s) used to read timestamp counter

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