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PROGRAM:

NAME


memusage - profile memory usage of a program

SYNOPSIS


memusage [option]... program [programoption]...

DESCRIPTION


memusage is a bash script which profiles memory usage of the program, program. It
preloads the libmemusage.so library into the caller's environment (via the LD_PRELOAD
environment variable; see ld.so(8)). The libmemusage.so library traces memory allocation
by intercepting calls to malloc(3), calloc(3), free(3), and realloc(3); optionally, calls
to mmap(2), mremap(2), and munmap(2) can also be intercepted.

memusage can output the collected data in textual form, or it can use memusagestat(1) (see
the -p option, below) to create a PNG file containing graphical representation of the
collected data.

Memory usage summary
The "Memory usage summary" line output by memusage contains three fields:

heap total
Sum of size arguments of all malloc(3) calls, products of arguments
(nmemb*size) of all calloc(3) calls, and sum of length arguments of all mmap(2)
calls. In the case of realloc(3) and mremap(2), if the new size of an
allocation is larger than the previous size, the sum of all such differences
(new size minus old size) is added.

heap peak
Maximum of all size arguments of malloc(3), all products of nmemb*size of
calloc(3), all size arguments of realloc(3), length arguments of mmap(2), and
new_size arguments of mremap(2).

stack peak
Before the first call to any monitored function, the stack pointer address
(base stack pointer) is saved. After each function call, the actual stack
pointer address is read and the difference from the base stack pointer
computed. The maximum of these differences is then the stack peak.

Immediately following this summary line, a table shows the number calls, total memory
allocated or deallocated, and number of failed calls for each intercepted function. For
realloc(3) and mremap(2), the additional field "nomove" shows reallocations that changed
the address of a block, and the additional "dec" field shows reallocations that decreased
the size of the block. For realloc(3), the additional field "free" shows reallocations
that caused a block to be freed (i.e., the reallocated size was 0).

The "realloc/total memory" of the table output by memusage does not reflect cases where
realloc(3) is used to reallocate a block of memory to have a smaller size than previously.
This can cause sum of all "total memory" cells (excluding "free") to be larger than the
"free/total memory" cell.

Histogram for block sizes
The "Histogram for block sizes" provides a breakdown of memory allocations into various
bucket sizes.

OPTIONS


-n name, --progname=name
Name of the program file to profile.

-p file, --png=file
Generate PNG graphic and store it in file.

-d file, --data=file
Generate binary data file and store it in file.

-u, --unbuffered
Do not buffer output.

-b size, --buffer=size
Collect size entries before writing them out.

--no-timer
Disable timer-based (SIGPROF) sampling of stack pointer value.

-m, --mmap
Also trace mmap(2), mremap(2), and munmap(2).

-?, --help
Print help and exit.

--usage
Print a short usage message and exit.

-V, --version
Print version information and exit.

The following options apply only when generating graphical output:

-t, --time-based
Use time (rather than number of function calls) as the scale for the X axis.

-T, --total
Also draw a graph of total memory use.

--title=name
Use name as the title of the graph.

-x size, --x-size=size
Make the graph size pixels wide.

-y size, --y-size=size
Make the graph size pixels high.

EXIT STATUS


Exit status is equal to the exit status of profiled program.

EXAMPLE


Below is a simple program that reallocates a block of memory in cycles that rise to a peak
before then cyclically reallocating the memory in smaller blocks that return to zero.
After compiling the program and running the following commands, a graph of the memory
usage of the program can be found in the file memusage.png:

$ memusage --data=memusage.dat ./a.out
...
Memory usage summary: heap total: 45200, heap peak: 6440, stack peak: 224
total calls total memory failed calls
malloc| 1 400 0
realloc| 40 44800 0 (nomove:40, dec:19, free:0)
calloc| 0 0 0
free| 1 440
Histogram for block sizes:
192-207 1 2% ================
...
2192-2207 1 2% ================
2240-2255 2 4% =================================
2832-2847 2 4% =================================
3440-3455 2 4% =================================
4032-4047 2 4% =================================
4640-4655 2 4% =================================
5232-5247 2 4% =================================
5840-5855 2 4% =================================
6432-6447 1 2% ================
$ memusagestat memusage.dat memusage.png

Program source
#include <stdio.h>
#include <stdlib.h>

#define CYCLES 20

int
main(int argc, char *argv[])
{
int i, j;
int *p;

printf("malloc: %zd\n", sizeof(int) * 100);
p = malloc(sizeof(int) * 100);

for (i = 0; i < CYCLES; i++) {
if (i < CYCLES / 2)
j = i;
else
j--;

printf("realloc: %zd\n", sizeof(int) * (j * 50 + 110));
p = realloc(p, sizeof(int) * (j * 50 + 100));

printf("realloc: %zd\n", sizeof(int) * ((j+1) * 150 + 110));
p = realloc(p, sizeof(int) * ((j + 1) * 150 + 110));
}

free(p);
exit(EXIT_SUCCESS);
}

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