---
name: "memleak-bpfcc"
section: "8"
platform: "linux"
package: "bpfcc-tools"
version: "0.31.0+ds-7"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/memleak-bpfcc"
---

# memleak-bpfcc(8)

Print a summary of outstanding allocations and their call stacks to detect memory leaks. Uses Linux eBPF/bcc.

## NAME

memleak - Print a summary of outstanding allocations and their call stacks to detect memory leaks. Uses Linux eBPF/bcc.

## SYNOPSIS

**memleak \[-h\] \[-p PID\] \[-t\] \[-a\] \[-o OLDER\] \[-c COMMAND\] \[--combined-only\]** \[--wa-missing-free\] \[-s SAMPLE\_RATE\] \[-T TOP\] \[-z MIN\_SIZE\] \[-Z MAX\_SIZE\] \[-O OBJ\] \[INTERVAL\] \[COUNT\]

## DESCRIPTION

memleak traces and matches memory allocation and deallocation requests, and collects call stacks for each allocation. memleak can then print a summary of which call stacks performed allocations that weren't subsequently freed.

When tracing a specific process, memleak instruments a list of allocation functions from libc, specifically: malloc, calloc, realloc, posix\_memalign, valloc, memalign, pvalloc, aligned\_alloc, and free. When tracing all processes, memleak instruments kmalloc/kfree, kmem\_cache\_alloc/kmem\_cache\_free, and also page allocations made by get\_free\_pages/free\_pages.

memleak may introduce significant overhead when tracing processes that allocate and free many blocks very quickly. See the OVERHEAD section below.

This tool only works on Linux 4.6+. Stack traces are obtained using the new BPF\_STACK\_TRACE\` APIs. For kernels older than 4.6, see the version under tools/old. Kernel memory allocations are intercepted through tracepoints, which are available on Linux 4.7+.

## REQUIREMENTS

CONFIG\_BPF and bcc.

## OPTIONS

- \-h

  Print usage message.

- \-p PID

  Trace this process ID only (filtered in-kernel). This traces libc allocator.

- \-t

  Print a trace of all allocation and free requests and results.

- \-a

  Print a list of allocations that weren't freed (and their sizes) in addition to their call stacks.

- \-o OLDER

  Print only allocations older than OLDER milliseconds. Useful to remove false positives. The default value is 500 milliseconds.

- \-c COMMAND

  Run the specified command and trace its allocations only. This traces libc allocator.

- \--combined-only

  Use statistics precalculated in kernel space. Amount of data to be pulled from kernel significantly decreases, at the cost of losing capabilities of time-based false positives filtering (-o).

- \--wa-missing-free

  Make up the action of free to alleviate misjudgments when free is missing.

- \-s SAMPLE\_RATE

  Record roughly every SAMPLE\_RATE-th allocation to reduce overhead.

- \-t TOP

  Print only the top TOP stacks (sorted by size). The default value is 10.

- \-z MIN\_SIZE

  Capture only allocations that are larger than or equal to MIN\_SIZE bytes.

- \-Z MAX\_SIZE

  Capture only allocations that are smaller than or equal to MAX\_SIZE bytes.

- \-O OBJ

  Attach to allocation functions in specified object instead of resolving libc. Ignored when kernel allocations are profiled.

- INTERVAL

  Print a summary of outstanding allocations and their call stacks every INTERVAL seconds. The default interval is 5 seconds.

- COUNT

  Print the outstanding allocations summary COUNT times and then exit.

## EXAMPLES

- Print outstanding kernel allocation stacks every 3 seconds:

  \# **memleak 3**

- Print user outstanding allocation stacks and allocation details for the process 1005:

  \# **memleak -p 1005 -a**

- Sample roughly every 5th allocation (~20%) of the call stacks and print the top 5

  stacks 10 times before quitting. # **memleak -s 5 --top=5 10**

- Run ./allocs and print outstanding allocation stacks for that process:

  \# **memleak -c ./allocs**

- Capture only allocations between 16 and 32 bytes in size:

  \# **memleak -z 16 -Z 32**

## OVERHEAD

memleak can have significant overhead if the target process or kernel performs allocations at a very high rate. Pathological cases may exhibit up to 100x degradation in running time. Most of the time, however, memleak shouldn't cause a significant slowdown. You can use the -s switch to reduce the overhead further by capturing only every N-th allocation. The -z and -Z switches can also reduce overhead by capturing only allocations of specific sizes.

Additionally, option --combined-only saves processing time by reusing already calculated allocation statistics from kernel. It's faster, but lacks information about particular allocations.

Also, option --wa-missing-free makes memleak more accuracy in the complicated environment.

To determine the rate at which your application is calling malloc/free, or the rate at which your kernel is calling kmalloc/kfree, place a probe with perf and collect statistics. For example, to determine how many calls to \_\_kmalloc are placed in a typical period of 10 seconds:

\# **perf probe '\_\_kmalloc'**

\# **perf stat -a -e 'probe:\_\_kmalloc' -- sleep 10**

## SOURCE

This is from bcc.

-

  https://github.com/iovisor/bcc

Also look in the bcc distribution for a companion \_examples.txt file containing example usage, output, and commentary for this tool.

## OS

Linux

## STABILITY

Unstable - in development.

## AUTHOR

Sasha Goldshtein