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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | BUGS | EXAMPLES | SEE ALSO | COLOPHON |
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memusage(1) General Commands Manual memusage(1)
memusage - profile memory usage of a program
memusage [option ...] program [programoption ...]
memusage is a bash(1) 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 (n*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 n*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.
-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.
The exit status of memusage is equal to the exit status of the
profiled program.
To report bugs, see ⟨http://www.gnu.org/software/libc/bugs.html⟩
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;
size_t size;
int *p;
size = sizeof(*p) * 100;
printf("malloc: %zu\n", size);
p = malloc(size);
for (i = 0; i < CYCLES; i++) {
if (i < CYCLES / 2)
j = i;
else
j--;
size = sizeof(*p) * (j * 50 + 110);
printf("realloc: %zu\n", size);
p = realloc(p, size);
size = sizeof(*p) * ((j + 1) * 150 + 110);
printf("realloc: %zu\n", size);
p = realloc(p, size);
}
free(p);
exit(EXIT_SUCCESS);
}
memusagestat(1), mtrace(1), ld.so(8)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.15 2025-05-17 memusage(1)
Pages that refer to this page: memusagestat(1), mtrace(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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