How to detect a memory leak?
I seem to have a larger memory leak on my current ubuntu System
After reporting strange Eclipse memory errors ( ) I started to get 'Not enough Memory' error messages in my console today - while doing simple tasks like typing in sudo -s - or even - free -m
Typing in 'free -m' repeadetly showed me how my RAM quickly goes up from 700M to 900M, growing up to the size of 2000M in a few seconds (after freeing up memory with echo 3 > /proc/sys/vm/drop_caches )
Eclipse isnt the cause, I completly killed the process and the ram still was going up. Is there any way to detect where the leak is coming from? I cant even update my system anymore, since apt-get update fails (probably because it's out of memory)
Using Ubuntu 11.10
6 Answers
First, make sure to have a temp folder available which has enough free space. The following commands create dumps which can be several GBs in size.
You can create a new tmp folder using the following command. You may want to change /tmp to a different filesystem with enough space
TMPDIR=$(mktemp -d -t -p /tmp)Steps to find Memory Leak
Find out the PID of the process which causing memory leak (you can also use e.g.
htopif available) and store it in a variable calledpidps -auxGiven that the PID is available in the variable
pid, you can capture the memory consumption using/proc/$pid/smapsand save into some file likebeforeMemInc.txt.cat /proc/$pid/smaps > $TMPDIR/beforeMemInc.txt- Wait some time for memory consumption to increase.
Capture
/proc/$pid/smapsagain and save it asafterMemInc.txtcat /proc/$pid/smaps > $TMPDIR/afterMemInc.txtFind the difference between first
smapsand 2ndsmaps, e. g. withdiff -u $TMPDIR/beforeMemInc.txt $TMPDIR/afterMemInc.txtNote down the address range where memory got increased, for example:
beforeMemInc.txt afterMemInc.txt --------------------------------------------------- 2b3289290000-2b3289343000 2b3289290000-2b3289343000 #ADDRESS Shared_Clean: 0 kB Shared_Clean: 0 kB Shared_Dirty: 0 kB Shared_Dirty: 0 kB Private_Clean: 0 kB Private_Clean: 0 kB Private_Dirty: 28 kB Private_Dirty: 36 kB Referenced: 28 kB Referenced: 36 kB Anonymous: 28 kB Anonymous: 36 kB #INCREASE MEM AnonHugePages: 0 kB AnonHugePages: 0 kB Swap: 0 kB Swap: 0 kB KernelPageSize: 4 kB KernelPageSize: 4 kB MMUPageSize: 4 kB MMUPageSize: 4 kB Locked: 0 kB Locked: 0 kB VmFlags: rd wr mr mw me ac VmFlags: rd wr mr mw me acUse GDB to dump memory on running process or get the coredump using
gcore -o $TMPDIR/process $PIDI used gdb on the running process to dump the memory to some file.
cd $TMPDIR gdb -p $pid dump memory memory.dump 0x2b3289290000 0x2b3289343000Now, use
stringscommand orhexdump -Cto print thememory.dumpstrings memory.dumpFrom this you get readable information which helps you locate those strings in your source code.
- Analyse your source to find the leak.
The drop_cache trick will not free memory, it will reset the cache. Uses ps command if you want to identify which processes uses the more memory.
For instance to monitor the list of the top 15 of resident memory users.
$ watch "ps --sort -rss -eo pid,pmem,rss,vsz,comm | head -16" PID %MEM RSS VSZ COMMAND 2590 13.4 136892 825000 firefox 1743 10.7 109020 300780 Xorg 2067 8.5 86764 1118140 unity-2d-shell 3307 4.1 42560 627780 unity-2d-spread 2068 2.9 29904 617644 unity-2d-panel 2092 2.5 25524 1291204 nautilus 2457 1.9 20292 530276 gnome-terminal 2351 1.9 20016 821488 unity-scope-vid 2161 1.9 19476 531968 unity-panel-ser 2034 1.7 18256 759716 gnome-settings- 2074 1.5 16176 518016 nm-applet 2273 1.5 15452 580416 unity-lens-vide 2051 1.4 15112 524260 metacity 2395 1.2 12836 407336 update-notifiYou could check also the shared memory reservation but you will only know who is the owner of the segments.
Pmap allocation:
$ ls -l /run/shm
total 272
-r-------- 1 ed ed 67108904 Nov 29 18:17 pulse-shm-1884617860
-r-------- 1 lightdm lightdm 67108904 Nov 29 18:11 pulse-shm-2352897759
-r-------- 1 ed ed 67108904 Nov 29 18:12 pulse-shm-3444873503
-r-------- 1 ed ed 67108904 Nov 29 18:12 pulse-shm-3485341848
-r-------- 1 lightdm lightdm 67108904 Nov 29 18:11 pulse-shm-535843976
-r-------- 1 ed ed 67108904 Nov 29 19:12 pulse-shm-789046959
-r-------- 1 ed ed 67108904 Nov 29 18:38 pulse-shm-863909656
$ df /run/shm
Filesystem 1K-blocks Used Available Use% Mounted on
none 509332 272 509060 1% /run/shmnote that reserved allocations are much higher than real the allocated pages (df 'used')
System V allocations :
$ ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x00000000 294912 ed 700 122880 2 dest
0x00000000 327681 ed 700 4823040 2 dest
0x00000000 491522 ed 600 393216 2 dest
0x00000000 589827 ed 700 4578120 2 dest
0x00000000 425988 ed 700 27852 2 dest
0x00000000 458757 ed 600 393216 2 dest Edit: Need to pass --sort -rss to ps to get the processes with the most memory usage, otherwise the process list is sorted increasing numerical and gives the processes with least memory usage.
memprof is a tool for profiling memory usage and finding memory leaks. It can generate a profile how much memory was allocated by each function in your program. Also, it can scan memory and find blocks that you’ve allocated but are no longer referenced anywhere.
memprof works by pre-loading a library to override the C library’s memory allocation functions and does not require you to recompile your program.
Source: Ubuntu Manual
0I have an older machine that I use that constantly spits out memory leak messages:
root@:~# free -m total used free shared buffers cached
Mem: 1898 1523 374 131 32 588
-/+ buffers/cache: 902 995
Swap: 1942 480 1462My script:
sync; sudo echo 3 > /proc/sys/vm/drop_cachesNamed it cache.sh
root@~# ./cache.sh
root@~# free -m total used free shared buffers cached
Mem: 1898 1106 791 126 1 207
-/+ buffers/cache: 897 1000
Swap: 1942 480 1462You can see I was down to 374 MB, ran the sync; sudo echo 3 > /proc/sys/vm/drop_caches and gained 417 MB back. One can cron it to run every 5 minutes or just have a terminal open and run it when you see slow performance. Yes, I need to add memory to the machine...
memstat is also a good tool that will show the amount of memory used by each block as well as how much memory is used by loaded libraries. Not the best tool but is worth using to gather details and statistics.
memstat -w -p pid is a good command to use.
I had a similar problem but with a very weird solution.
For some unknown reason I had a mail server on my laptop setup and running.I don't know why I had it...However I shut its service down and it turned out that that software on my laptop was under a ddos attack.After that everything was normal.
