plan9fox/sys/man/1/leak

.TH LEAK 1
.SH NAME
leak, kmem, umem \- help find memory leaks
.SH SYNOPSIS
.B leak
[
.B -abcds
]
[
.B -f
.I binary
]
[
.B -r
.I res
]
[
.B -x
.I width
]
.I pid ...
.PP
.B kmem
[
.I kernel
]
.PP
.B umem
.I pid
[
.I textfile
]
.SH DESCRIPTION
.I 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 pointers.
The set of root pointers is created by looking through
the shared bss segment as well as each process's registers.
.PP
Unless directed otherwise,
.I leak
prints, for each block, a line with seven space-separated fields:
the string
.BR 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
.IR malloc (2)),
useful for finding who allocated the leaked blocks.
.PP
If the
.B -s
or the
.B -c
option is given,
.I leak 
will instead present a sequence of
.IR acid (1)
commands that show each leaky allocation site.
With
.B -s
a comment appears next to each command to 
indicate how many lost blocks were allocated
at that point in the program.
With
.B -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.
.PP
If the
.B -a
option is given,
.I leak 
will print information as decribed above,
but for all allocated blocks,
not only leaked ones.
If the
.B -d
option is given,
.I leak 
will print information as decribed above,
but for all free blocks,
i.e. those freed,
or those that are not yet
in use (fragmentation?).
The
.B -a
and
.B -d
options can be combined.
.PP
If the
.B -b
option is given,
.I leak
will print a Plan 9 image file
graphically summarizing the memory arenas.
In the image, each pixel represents
.I res
(default 8)
bytes.
The color code is:
.TP "\w'\fIbright blue\fR   'u
.I "dark blue
Completely allocated.
.TP
.I "bright blue
Contains malloc headers.
.TP
.I "bright red
Contains malloc headers for leaked memory.
.TP
.I "dark red
Contains leaked memory.
.TP
.I "yellow
Completely free
.TP
.I "white
Padding to fill out the image.
.PD
The bright pixels representing headers help in 
counting the number of blocks.
Magnifying the images with
.IR lens (1)
is often useful.
.PP
If given a name rather than a list of process ids,
.I leak
echoes back a command-line with process ids of every process
with that name.
.PP
The
.B -f
option specifies a binary to go on the 
.IR acid (1)
command-line used to inspect the
processes, and is only necessary
when inspecting processes started
from stripped binaries.
.PP
.I Umem
prints a summary of all allocated blocks in the process with id
.IR 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.
.I Umem
prints summarizes all allocations, not just 
memory leaks, but it is faster and requires less memory than 
.I leak .
.PP
.I Kmem
is like
.I umem
but prints a summary for the running kernel.
.SH EXAMPLES
List lost blocks in 
.IR 8.out .
This depends on the fact that there is only
once instance of 
.I 8.out
running; if there were more, the output of
.B "leak -s 8.out
would need editing before sending to the shell.
.IP
.EX
% leak -s 8.out
leak -s 229 230
% leak -s 8.out | rc
src(0x0000bf1b); // 64
src(0x000016f5); // 7
src(0x0000a988); // 7
%
.EE
.LP
View the memory usage graphic for the window system.
.IP
.EX
% leak -b rio | rc | page
.EE
.PP
List the top allocation points in the kernel,
first by count and then by total size:
.IP
.EX
% kmem | sed 10q
% kmem | sort -nr +1 | sed 10q
.EE
.SH SOURCE
.B /sys/lib/acid/leak
.br
.B /sys/src/cmd/aux/acidleak.c
.br
.B /rc/bin/leak
.br
.B /rc/bin/kmem
.br
.B /rc/bin/umem
.SH SEE ALSO
.IR getcallerpc (2),
.I setmalloctag
in
.IR malloc (2)
.SH BUGS
.I Leak
and
.I kmem
depend on the internal structure of the
libc pool memory allocator (see 
.IR pool (2)).
Since the ANSI/POSIX environment uses a different
allocator,
.I leak
will not work on APE programs.
.PP
.I Leak
is not speedy, and
.I acidleak
can consume more memory than the process(es) being examined.
.PP
These commands require
.B /sys/src/libc/port/pool.acid
to be present and generated from
.BR pool.c .