system call enables or disables
program counter profiling of the current process.
If profiling is enabled,
then at every profiling clock tick,
the kernel updates an appropriate count in the
The frequency of the profiling clock is recorded
in the header in the profiling output file.
bytes and is divided into
a series of 16-bit bins.
Each bin counts the number of times the program counter
was in a particular address range in the process
when a profiling clock tick occurred while profiling was enabled.
For a given program counter address,
the number of the corresponding bin is given
by the relation:
[(pc - offset) / 2] * scale / 65536
argument is the lowest address at which
the kernel takes program counter samples.
argument ranges from 1 to 65536 and
can be used to change the span of the bins.
A scale of 65536 maps each bin to 2 bytes of address range;
a scale of 32768 gives 4 bytes, 16384 gives 8 bytes and so on.
Intermediate values provide approximate intermediate ranges.
value of 0 disables profiling.