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QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
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C
ClockCycles()
Get the number of clock cycles

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
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        Invalidate cache lines associated with a data buffer
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        Flush the data cache and/or invalidate the instruction and/or the data cache.
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        Compute the complex arc cosine
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        Compute the complex inverse hyperbolic cosine
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        Allocate space for an array
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        Compute the argument of a complex number
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        Compute the complex arc sine
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        Compute the complex inverse hyperbolic sine
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        Compute the complex arc tangent
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        Compute the complex inverse hyperbolic tangent
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        Compute the cube root of a number
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        Compute the complex cosine
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        Compute the complex hyperbolic cosine
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        Round up a value to the next integer
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        Compute the complex base-e exponential of a complex number
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        Return the input baud rate that's stored in a termios structure
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        Return the output baud rate that's stored in a termios structure
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        Set terminal attributes
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        Set the input baud rate in a termios structure
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        Set the output baud rate in a termios structure
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        Create a communications channel
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        Change the properties of a channel
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        Destroy a communications channel
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        Change the current working directory
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        Change the permissions for a file
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        Change the user ID and group ID of a file
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        Change the root directory
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        Compute the imaginary part of a complex number
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        Clear the environment
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        Clear a stream's end-of-file and error flags
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        Set to NULL the prefix for the networking stack path for the current thread
      - ClientInfoExtFree()
        Free the structure used for extended information about a client connection
      - clock()
        Return the number of clock ticks used by the program
      - clock_getcpuclockid()
        Return the clock ID of the CPU-time clock from a specified process
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        Get the resolution of the clock
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        Get the current time of a clock
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        Get the time of a clock, in nanoseconds
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        Suspend a thread until a timeout or signal occurs, using a specified clock
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        Set a clock
      - ClockAdjust(), ClockAdjust_r()
        Adjust the time of a clock
      - ClockCycles()
        Get the number of clock cycles
      - ClockId(), ClockId_r()
        Get the CPU-time clock ID for a given process and thread
      - ClockPeriod(), ClockPeriod_r()
        Get a clock period
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        Get or set a clock
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        Compute the complex natural (base-e) logarithm of a complex number
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        Close a file
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        Close a directory
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        Close the slogger2 system log
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        Find the path used to invoke the current process
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        Create a complex number from its real and imaginary parts
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        Unblock threads waiting on a condition
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        Destroy a condition variable
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        Initialize a condition variable
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        Unblock a thread that's waiting on a condition variable
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        Wait on a condition variable, with a time limit
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        Wait on a condition variable
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        Get configuration-defined string values
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        Compute the complex conjugate of a complex number
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        Establish a connection between a process and a channel
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        Get information about a client connection
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        Get extended information about a client connection, including abilities
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        Get extended information about a client connection
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        Break a connection between a process and a channel
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        Support file descriptor duplication
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        Modify or query the flags associated with a connection
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        Get information about a server connection
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        Copy the sign bit from one number to another
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        Compute the cosine of an angle
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        Compute the hyperbolic cosine
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        Raise a complex number to the power of another complex number
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        Compute the projection of a complex number on the Riemann sphere
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        Compute the real part of a complex number
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        Create and open a file (low-level)
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        Hash a password
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        Compute the complex sine
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        Compute the complex hyperbolic sine
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        Compute the square root of a complex number
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        Compute the complex tangent
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        Compute the complex hyperbolic tangent
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        Generate the path name of the current controlling terminal
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        Convert calendar time to local time
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Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

ClockCycles()

QNX SDP8.0C Library ReferenceAPIDeveloper

Get the number of clock cycles

Synopsis:

#include <sys/neutrino.h>
#include <inttypes.h>

uint64_t ClockCycles( void );

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The ClockCycles() function returns the current value of a free-running 64-bit cycle counter. This is implemented on each processor architecture as a high-performance mechanism for timing short intervals. On x86 systems, ClockCycles() reads the Time Stamp Counter (RDTSC); on ARM systems, it reads the Generic Timer (CNTVCT_EL0 register).

You can use the SYSPAGE_ENTRY(qtime)->cycles_per_sec field to get the number of ClockCycles() increments in one second.

Note:

QNX OS requires that the hardware underlying ClockCycles() be synchronized across all processors on a multicore system. Here, synchronized means that the difference in time values (i.e., deltas) measured by different processors must be small enough to be not software observable. This requirement means that you don't have to call ThreadCtl( _NTO_TCTL_RUNMASK, ...) to prevent threads from migrating to another processor between calls to ClockCycles().

Unless you specify the frequency for ClockCycles() via the startup -f option, startup determines a frequency value on each target bootup. On AArch64 startup reads a hardware register that contains the frequency, thus it is correct and consistent across boots. On x86_64 the value determined is not exact and may vary from boot to boot. To ensure consistent results, we recommend that you query your x86_64 hardware for the frequency, or consult your target's documentation. Once you determine the frequency, you can either specify this value in your target configuration by using the startup -f option, or modify startup to hard-code the frequency.

Having a correct value is important to ensure proper OS behavior for time and timers. For more information, see startup-* options in the Utilities Reference guide.

Blocking states:

This call doesn't block.

Returns

The current value of a free-running 64-bit cycle counter.

Examples:

See SYSPAGE_ENTRY().

Classification:


Safety:
Cancellation point	No
Signal handler	Yes
Thread	Yes

Page updated: December 04, 2024