NAME

leak − examine family of processes for memory leaks

SYNOPSIS

­leak [ ­-bs ] [ ­-f ­binary ] [ ­-r ­res ] [ ­-x ­width ] ­pid ... 

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 pointers.  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 five space-separated fields: the string block, the address of the block, the size of the block, and 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 option is given, ­leak will instead present a sequence of acid(1) commands that show each leaky allocation site. A comment appears next to each command to indicate how many lost blocks were allocated at that point in the program.

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. 

­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 necessary when inspecting processes started from stripped binaries.

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. 

g% leak -s 8.out
leak -s 229 230
g% leak -s 8.out | rc
src(0x0000bf1b); // 64
src(0x000016f5); // 7
src(0x0000a988); // 7
g%

View the memory usage graphic for the window system. 

g% leak -b rio | rc | page

SOURCE

­/sys/lib/acid/leak
­/sys/src/cmd/aux/acidleak.c
­/rc/bin/leak

BUGS

Leak depends 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.

Plan 9  —  March 29, 2002