int
profil(
char *samples
, size_t size
, u_long offset
, u_int scale
)
)
function enables or disables
program counter profiling of the current process.
If profiling is enabled,
then at every clock tick,
the kernel updates an appropriate count in the
samples
buffer.
The buffer
samples
contains
size
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 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
The
offset
parameter is the lowest address at which
the kernel takes program counter samples.
The
scale
parameter 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.
A
scale
value of 0 disables profiling.
scale
value is nonzero and the buffer
samples
contains an illegal address,
profil(
)
returns -1,
profiling is terminated and
errno
is set appropriately.
Otherwise
profil(
)
returns 0.
/usr/lib/gcrt0.o
gmon.out
EFAULT
]
samples
contains an invalid address.
).
The
samples
argument should really be a vector of type
unsigned short
.
The format of the gmon.out file is undocumented.