I have a server with 12G of memory. A fragment of top is shown below:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
12979 frank 20 0 206m 21m 12m S 11 0.2 26667:24 krfb
13 root 15 -5 0 0 0 S 1 0.0 36:25.04 ksoftirqd/3
59 root 15 -5 0 0 0 S 0 0.0 4:53.00 ata/2
2155 root 20 0 662m 37m 8364 S 0 0.3 338:10.25 Xorg
4560 frank 20 0 8672 1300 852 R 0 0.0 0:00.03 top
12981 frank 20 0 987m 27m 15m S 0 0.2 45:10.82 amarok
24908 frank 20 0 16648 708 548 S 0 0.0 2:08.84 wrapper
1 root 20 0 8072 608 572 S 0 0.0 0:47.36 init
2 root 15 -5 0 0 0 S 0 0.0 0:00.00 kthreadd
The free -m shows the following:
total used free shared buffers cached
Mem: 12038 11676 362 0 599 9745
-/+ buffers/cache: 1331 10706
Swap: 2204 257 1946
If I understand correctly, the system has only 362 MB of available memory. My question is: How can I find out which process is consuming most of the memory?
Just as background info, the system is running 64bit OpenSuse 12.
First, repeat this mantra for a little while: "unused memory is wasted memory". The Linux kernel keeps around huge amounts of file metadata and files that were requested, until something that looks more important pushes that data out. It's why you can run:
find /home -type f -name '*.mp3'
find /home -type f -name '*.aac'
and have the second find instance run at ridiculous speed.
Linux only leaves a little bit of memory 'free' to handle spikes in memory usage without too much effort.
Second, you want to find the processes that are eating all your memory; in top use the M command to sort by memory use. Feel free to ignore the VIRT column, that just tells you how much virtual memory has been allocated, not how much memory the process is using. RES reports how much memory is resident, or currently in ram (as opposed to swapped to disk or never actually allocated in the first place, despite being requested).
But, since RES will count e.g. /lib/libc.so.6 memory once for nearly every process, it isn't exactly an awesome measure of how much memory a process is using. The SHR column reports how much memory is shared with other processes, but there is no guarantee that another process is actually sharing -- it could be sharable, just no one else wants to share.
The smem tool is designed to help users better gage just how much memory should really be blamed on each individual process. It does some clever work to figure out what is really unique, what is shared, and proportionally tallies the shared memory to the processes sharing it. smem may help you understand where your memory is going better than top will, but top is an excellent first tool.
use quick tip using top command in linux/unix
$ top
and then hit Shift+m (i.e. write a capital M).
From man top
SORTING of task window
For compatibility, this top supports most of the former top sort keys.
Since this is primarily a service to former top users, these commands do
not appear on any help screen.
command sorted-field supported
A start time (non-display) No
M %MEM Yes
N PID Yes
P %CPU Yes
T TIME+ Yes
Or alternatively: hit Shift + f , then choose the display to order by memory usage by hitting key n then press Enter. You will see active process ordered by memory usage
ps aux | awk '{print $2, $4, $11}' | sort -k2rn | head -n 10
(Adding -n numeric flag to sort command.)
First you should read an explanation on the output of free. Bottom line: you have at least 10.7 GB of memory readily usable by processes.
Then you should define what "memory usage" is for a process (it's not easy or unambiguous, trust me).
Then we might be able to help more :-)
List and Sort Processes by Memory Usage:
ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS
ps aux --sort '%mem'
from procps' ps (default on Ubuntu 12.04) generates output like:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
...
tomcat7 3658 0.1 3.3 1782792 124692 ? Sl 10:12 0:25 /usr/lib/jvm/java-7-oracle/bin/java -Djava.util.logging.config.file=/var/lib/tomcat7/conf/logging.properties -D
root 1284 1.5 3.7 452692 142796 tty7 Ssl+ 10:11 3:19 /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
ciro 2286 0.3 3.8 1316000 143312 ? Sl 10:11 0:49 compiz
ciro 5150 0.0 4.4 660620 168488 pts/0 Sl+ 11:01 0:08 unicorn_rails worker[1] -p 3000 -E development -c config/unicorn.rb
ciro 5147 0.0 4.5 660556 170920 pts/0 Sl+ 11:01 0:08 unicorn_rails worker[0] -p 3000 -E development -c config/unicorn.rb
ciro 5142 0.1 6.3 2581944 239408 pts/0 Sl+ 11:01 0:17 sidekiq 2.17.8 gitlab [0 of 25 busy]
ciro 2386 3.6 16.0 1752740 605372 ? Sl 10:11 7:38 /usr/lib/firefox/firefox
So here Firefox is the top consumer with 16% of my memory.
You may also be interested in:
ps aux --sort '%cpu'
you can specify which column to sort by, with following steps:
steps:
* top
* shift + F
* select a column from the list
e.g. n means sort by memory,
* press enter
* ok
You can see memory usage by executing this code in your terminal:
$ watch -n2 free -m
$ htop
You have this simple command:
$ free -h
来源：https://stackoverflow.com/questions/4802481/how-to-see-top-processes-sorted-by-actual-memory-usage