I recently discovered valgrind while searching for a way to see how much
memory (total memory footprint) my small program represented.
I was perplexed by the results I was seeing, since I expected at most to
use perhaps tens of thousands of bites not Millions. My application is not
dynamically requesting/allocating memory, all memory consumed is in the
form of statically assigned character arrays, automatic stack usage etc..
valgrind --version
valgrind-3.9.0
I'm running on LFS 7.4
linux-3.11
glibc-2.18
gcc-4.8.1
So I did a test by running valgrind against an empty C program. The program
does nothing but return. Can someone explain why the output shows
continually increasing memory used and in total over a 6 MB peak?
user [ ~/ccode/string_buffer ]> cat > ./just_return.c << "EOF"
> int main(void)
> {
> return 0;
> }
> EOF
user [ ~/ccode/string_buffer ]> gcc -O0 -Wall -g -o just_return
just_return.c
user [ ~/ccode/string_buffer ]> valgrind --tool=massif --pages-as-heap=yes
--time-unit=B ./just_return
==11740== Massif, a heap profiler
==11740== Copyright (C) 2003-2013, and GNU GPL'd, by Nicholas Nethercote
==11740== Using Valgrind-3.9.0 and LibVEX; rerun with -h for copyright info
==11740== Command: ./just_return
==11740==
==11740==
user [ ~/ccode/string_buffer ]> ms_print massif.out.11740
--------------------------------------------------------------------------------
Command: ./just_return
Massif arguments: --pages-as-heap=yes --time-unit=B
ms_print arguments: massif.out.11740
--------------------------------------------------------------------------------
MB
5.902^
:
| #
| #
| #
| #
| #
| #
| #
| #
| #
| #
| #
| #
|
:::::::::::::::::::::::::::::::::::::::::::::#
|
: #
|
: #
|
: #
|
: #
|
: #
|
: #
0
+----------------------------------------------------------------------->MB
0
5.918
Number of snapshots: 21
Detailed snapshots: [9, 19 (peak)]
--------------------------------------------------------------------------------
n time(B) total(B) useful-heap(B) extra-heap(B)
stacks(B)
--------------------------------------------------------------------------------
0 4,096 4,096 4,096
0 0
1 8,192 8,192 8,192
0 0
2 139,264 139,264 139,264
0 0
3 147,456 147,456 147,456
0 0
4 151,552 151,552 151,552
0 0
5 155,648 155,648 155,648
0 0
6 159,744 159,744 159,744
0 0
7 167,936 167,936 167,936
0 0
8 172,032 172,032 172,032
0 0
9 172,032 172,032 172,032
0 0
100.00% (172,032B) (page allocation syscalls) mmap/mremap/brk, --alloc-fns,
etc.
->100.00% (172,032B) 0xFFFFFFFFFFFFFFFF: ???
--------------------------------------------------------------------------------
n time(B) total(B) useful-heap(B) extra-heap(B)
stacks(B)
--------------------------------------------------------------------------------
10 176,128 176,128 176,128
0 0
11 2,277,376 2,277,376 2,277,376
0 0
12 2,281,472 2,281,472 2,281,472
0 0
13 2,297,856 2,297,856 2,297,856
0 0
14 6,139,904 6,139,904 6,139,904
0 0
15 6,164,480 6,164,480 6,164,480
0 0
16 6,180,864 6,180,864 6,180,864
0 0
17 6,184,960 6,184,960 6,184,960
0 0
18 6,189,056 6,189,056 6,189,056
0 0
19 6,201,344 6,176,768 6,176,768
0 0
100.00% (6,176,768B) (page allocation syscalls) mmap/mremap/brk,
--alloc-fns, etc.
->97.21% (6,004,736B) 0x4017119: mmap (in /lib/ld-2.18.so)
| ->96.22% (5,943,296B) 0x40064F0: _dl_map_object_from_fd (in /lib/
ld-2.18.so)
| | ->96.22% (5,943,296B) 0x4007F93: _dl_map_object (in /lib/ld-2.18.so)
| | ->62.20% (3,842,048B) 0x400C230: openaux (in /lib/ld-2.18.so)
| | | ->62.20% (3,842,048B) 0x400E682: _dl_catch_error (in /lib/ld-2.18.so
)
| | | ->62.20% (3,842,048B) 0x400C483: _dl_map_object_deps (in /lib/
ld-2.18.so)
| | | ->62.20% (3,842,048B) 0x4002D52: dl_main (in /lib/ld-2.18.so)
| | | ->62.20% (3,842,048B) 0x40150B3: _dl_sysdep_start (in /lib/
ld-2.18.so)
| | | ->62.20% (3,842,048B) 0x40049A4: _dl_start (in /lib/
ld-2.18.so)
| | | ->62.20% (3,842,048B) 0x4001136: ??? (in /lib/ld-2.18.so)
| | |
| | ->34.02% (2,101,248B) 0x400131C: map_doit (in /lib/ld-2.18.so)
| | ->34.02% (2,101,248B) 0x400E682: _dl_catch_error (in /lib/ld-2.18.so
)
| | ->34.02% (2,101,248B) 0x4000F78: do_preload (in /lib/ld-2.18.so)
| | ->34.02% (2,101,248B) 0x40040C6: dl_main (in /lib/ld-2.18.so)
| | ->34.02% (2,101,248B) 0x40150B3: _dl_sysdep_start (in /lib/
ld-2.18.so)
| | ->34.02% (2,101,248B) 0x40049A4: _dl_start (in /lib/
ld-2.18.so)
| | ->34.02% (2,101,248B) 0x4001136: ??? (in /lib/ld-2.18.so)
| |
| ->00.99% (61,440B) in 1+ places, all below ms_print's threshold (01.00%)
|
->02.79% (172,032B) 0xFFFFFFFFFFFFFFFF: ???
--------------------------------------------------------------------------------
n time(B) total(B) useful-heap(B) extra-heap(B)
stacks(B)
--------------------------------------------------------------------------------
20 6,205,440 6,172,672 6,172,672
0 0
Thanks,
Rob Taylor
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