LEAK(1) LEAK(1)
NAME
leak, kmem, umem - help find memory leaks
SYNOPSIS
leak [ -abcds ] [ -f binary ] [ -r res ] [ -x width ] pid
...
kmem [ kernel ]
umem pid [ textfile ]
DESCRIPTION
Leak examines the named processes, which should be sharing
their data and bss segments, for memory leaks. It uses a
mark and sweep-style algorithm to determine which allocated
blocks are no longer reachable from the set of root point-
ers. The set of root pointers is created by looking through
the shared bss segment as well as each process's registers.
Unless directed otherwise, leak prints, for each block, a
line with seven space-separated fields: the string block,
the address of the block, the size of the block, the first
two words of the block, and the function names represented
by the first two words of the block. Usually, the first two
words of the block contain the malloc and realloc tags (see
malloc(2)), useful for finding who allocated the leaked
blocks.
If the -s or the -c option is given, leak will instead pre-
sent a sequence of acid(1) commands that show each leaky
allocation site. With -s a comment appears next to each
command to indicate how many lost blocks were allocated at
that point in the program. With -c the comments are
extended to indicate also the total number of bytes lost at
that point in the program, and an additional comment line
gives the overall total number of bytes.
If the -a option is given, leak will print information as
decribed above, but for all allocated blocks, not only
leaked ones. If the -d option is given, leak will print
information as decribed above, but for all free blocks, i.e.
those freed, or those that are not yet in use (fragmenta-
tion?). The -a and -d options can be combined.
If the -b option is given, leak will print a Plan 9 image
file graphically summarizing the memory arenas. In the
image, each pixel represents res (default 8) bytes. The
color code is:
dark blue Completely allocated.
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LEAK(1) LEAK(1)
bright blue Contains malloc headers.
bright red Contains malloc headers for leaked memory.
dark red Contains leaked memory.
yellow Completely free
white Padding to fill out the image. The bright
pixels representing headers help in counting
the number of blocks. Magnifying the images
with lens(1) is often useful.
If given a name rather than a list of process ids, leak
echoes back a command-line with process ids of every process
with that name.
The -f option specifies a binary to go on the acid(1)
command-line used to inspect the processes, and is only nec-
essary when inspecting processes started from stripped bina-
ries.
Umem prints a summary of all allocated blocks in the process
with id pid. Each line of the summary gives the count and
total size of blocks allocated at an allocation point. The
list is sorted by count in decreasing order. Umem prints
summarizes all allocations, not just memory leaks, but it is
faster and requires less memory than leak .
Kmem is like umem but prints a summary for the running ker-
nel.
EXAMPLES
List lost blocks in 8.out. This depends on the fact that
there is only once instance of 8.out running; if there were
more, the output of leak -s 8.out would need editing before
sending to the shell.
% leak -s 8.out
leak -s 229 230
% leak -s 8.out | rc
src(0x0000bf1b); // 64
src(0x000016f5); // 7
src(0x0000a988); // 7
%
View the memory usage graphic for the window system.
% leak -b rio | rc | page
List the top allocation points in the kernel, first by count
and then by total size:
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LEAK(1) LEAK(1)
% kmem | sed 10q
% kmem | sort -nr +1 | sed 10q
SOURCE
/sys/lib/acid/leak
/sys/src/cmd/aux/acidleak.c
/rc/bin/leak
/rc/bin/kmem
/rc/bin/umem
SEE ALSO
getcallerpc(2), setmalloctag in malloc(2)
BUGS
Leak and kmem depend on the internal structure of the libc
pool memory allocator (see pool(2)). Since the ANSI/POSIX
environment uses a different allocator, leak will not work
on APE programs.
Leak is not speedy, and acidleak can consume more memory
than the process(es) being examined.
These commands require /sys/src/libc/port/pool.acid to be
present and generated from pool.c.
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