memleax
memleax
debugs memory leak of a running process by attaching it,
without recompiling or restarting.
status
Stable and completed.
memleax
is a tool with single and clear aim. There is
no known bug to fix and no new feature to add by now.
However if you get any new feature or bug, please report to GitHub, or mail to me.
how it works
memleax
debugs memory leak of a running process by attaching it.
It hooks the target process's invocation of memory allocation and free,
and reports the memory blocks which live long enough as memory leak, in real time.
The default expire threshold is 10 seconds, however you should always
set it by -e
option according to your scenarios.
It is very convenient to use, and suitable for production environment.
There is no need to recompile the program or restart the target process.
You run memleax
to monitor the target process, wait for the real-time memory
leak report, and then kill it (e.g. by Ctrl-C) to stop monitoring.
memleax
follows new threads, but not forked processes.
If you want to debug multiple processes, just run multiple memleax
.
performance impact
Because target process's each invocation of memory allocation and free makes a TRAP, the performance impact depends on the frequency of memory invocation in target process.
For example, it impacts lightly to nginx
with HTTP, while heavily with HTTPS,
because OpenSSL
calls malloc()
terribly.
difference from Valgrind
-
Valgrind
starts target process, whilememleax
attaches to a running process; -
Valgrind
gives memory leak report after target process quits, whilememleax
reports in real time; -
Valgrind
reports all unfreed memory include program init, whilememleax
reports only after attaching, skipping the init phase; -
Valgrind
runs target process on its virtual CPU, which makes it slow. Whilememleax
hooks memory APIs, which may be less slow if the target process call memory APIs not often. -
Valgrind
debugs kinds of memory bugs, whilememleax
is lightweight and only detects memory leak.
In summary, I think Valgrind
is more powerful, while memleax
is more
convenient and suitable for production environment.
licence
GPLv2
OS-machine
GNU/Linux
atx86
andx86_64
, tested on CentOS 7.2 and Ubuntu 16.04GNU/Linux
atarmv7
andaarch64
, tested on Raspbian and pi64.FreeBSD
ati386
andamd64
, tested on FreeBSD 10.3
NOTE: If memleax
can not show function backtrace on GNU/Linux
at aarch64
,
you could try to compile the target program with -funwind-tables
flag of GCC.
install by package
There are DEB and RPM packages for releases.
For Arch Linux users, memleax
is available in AUR. Thanks to jelly.
For FreeBSD users, memleax
is available in FreeBSD Ports Collection.
Thanks to tabrarg.
I tried to submit memleax
to Fedora EPEL,
but failed. Any help is welcomed.
build from source
The development packages of the following libraries are required:
libunwind
libelf
libdw
orlibdwarf
.libdw
is preferred. They are used to read dwarf debug-line information. If you do not have them neither, set--disable-debug_line
toconfigure
to disable it. As a result you will not see file name and line number in backtrace.
These packages may have different names in different distributions, such as
libelf
may names libelf
, elfutils-libelf
, or libelf1
.
NOTE: On FreeBSD 10.3, there are built-in libelf
and libdwarf
already.
However another libelf
and libdwarf
still can be installed by pkg
.
memleax
works with built-in libelf
and pkg libdwarf
. So you should
install libdwarf
by pkg
, and must not install libelf
by pkg
.
After all required libraries are installed, run
$ ./configure
$ make
$ sudo make install
usage
start
To debug a running process, run:
$ memleax [options] <target-pid>
then memleax
begins to monitor the target process, and report memory leak in real time.
You should always set expire time by -e
options according to your scenarios.
For example, if you are debugging an HTTP server with keepalive, and there are
connections last for more than 5 minutes, you should set -e 360
to cover it.
If your program is expected to free every memory in 1 second, you should set -e 2
to get report in time.
wait and check the report
The memory blocks live longer than the threshold, are showed as:
CallStack[3]: memory expires with 101 bytes, backtrace:
0x00007fd322bd8220 libc-2.17.so malloc()+0
0x000000000040084e test foo()+14 foo.c:12
0x0000000000400875 test bar()+37 bar.c:20
0x0000000000400acb test main()+364 test.c:80
CallStack[3]
is the ID of CallStack where memory leak happens.
The backtrace is showed only on the first time, while it only shows the ID and counter if expiring again:
CallStack[3]: memory expires with 101 bytes, 2 times again
If the expired memory block is freed later, it shows:
CallStack[6]: expired-memory frees after 10 seconds
If there are too many expired-memory-blocks are freed on one CallStack, this CallStack will not be showed again:
Warning: too many expired-free at CallStack[6]. will not show this CallStack later
When you think you have found the answer, stop the debug.
stop
memleax
quits on:
- you stop it, by Ctrl-C or kill,
- the target process quits,
- too many leaks at one CallStack (option -m), or
- too many CallStacks with memory leak (option -c).
After quitting, it also gives statistics for the CallStacks with memory leak:
CallStack[3]: may-leak=20 (2020 bytes)
expired=20 (2020 bytes), free_expired=0 (0 bytes)
alloc=20 (2020 bytes), free=0 (0 bytes)
freed memory live time: min=0 max=0 average=0
un-freed memory live time: max=20
0x00007fd322bd8220 libc-2.17.so malloc()+0
0x000000000040084e test foo()+14 foo.c:12
0x0000000000400875 test bar()+37 bar.c:20
0x0000000000400acb test main()+364 test.c:80