my RAM got filled completely, and the buff/cache occupied all the memory pl z do let me know how to make it clear when I run the command free -m I get this output,
this is a Linux VM made on azure for WordPress bitnami
$ free -m
total used free shared buff/cache available
Mem: 64320 19319 3164 115 41837 44168
Swap: 0
image
I tried to reproduce the same in my environment I got some buff/cache like below.
To clear the buff/cache try to use the below command.
Every Linux has three options to clear cache
First - clear page cache only
echo 1 > /proc/sys/vm/drop_caches
Second - clear dentries and inodes
echo 2 > /proc/sys/vm/drop_caches
Third - clear page cache and dentries and inodes
echo 3 > /proc/sys/vm/drop_caches
When I try to run this above script, there is 912M of total RAM, and 144M as used. And before I have 352M as free after exciting the script my buff/cache were reduced from 415 to 58 and free Ram increased upto 708M
Reference:
Clear RAM Memory Cache, Buffer, and Swap Space on Linux Credits by Arpit-saini
I'm trying to run a simulation on my local computer in university, but after some iterations it's being killed by a SIGKILL. Even when I check the available swap space it shows that still I have enough space !!!
:~$ free -m
total used free shared buffers cached
Mem: 3937 2091 1845 0 64 677
-/+ buffers/cache: 1349 2587
Swap: 3860 738 3122
The same story repeats when I use another server by ssh
:~$ free -m
total used free shared buffers cached
Mem: 129043 98281 30761 52 4 32901
-/+ buffers/cache: 65375 63668
Swap: 4095 120 3975
When I run it on my own laptop it works properly.
I'd really appreciate if help me out.
Are you checking the swap space after the fact or during the run? If there is a memory crunch the operating system's out of memory killer (OOM Killer) may kill the process ( depending on the configuration this could be the worst offender, random or anything else). Execute "sar" command and see the system state around the time your process got killed.
I know there are page cache and buffer cache in Linux. Page cache is for file system, and buffer cache is for device.
To free pagecache:
echo 1 > /proc/sys/vm/drop_caches
To free dentries and inodes:
echo 2 > /proc/sys/vm/drop_caches
To free pagecache, dentries and inodes:
echo 3 > /proc/sys/vm/drop_caches
My question:
Is buffer cache covered in drop_caches?
If not, then is there a method to only free buffer caches, leaving the page cache still cached?
If there isn't, why it's unnecessary or impossible?
Ans:-
sync; echo 3 > /proc/sys/vm/drop_caches
Here’s the output of free before and after running the above command.
Before
# free -m
total used free shared buffers cached
Mem: 502 487 15 0 15 170
-/+ buffers/cache: 301 201
Swap: 3153 375 2777
After
# free -m
total used free shared buffers cached
Mem: 502 345 157 0 1 44
-/+ buffers/cache: 300 202
As you can see the highlighted numbers, the buffers and cached values have dropped significantly after I ran the command. Again, this is not necessary. In fact, it’s not recommended at all but there it is if you’re curious to know.
I'm running Ubuntu Trusty 14.04 on a new machine with 8GB of RAM, and it seems to be locking up periodically and nothing is in syslog file. I've installed Nagios and have been watching the graphs, and it looks like memory is going high from 7% to 72% in just a span of 10 mins. Only node process are running on server. In top I found all process are running very normal memory consumption. Even after stopping node process. Memory remains with same utilization.
free agrees, claiming I'm using more than 5.7G of memory:
free -h
total used free shared buffers cached
Mem: 7.8G 6.5G 1.3G 2.2M 233M 612M
-/+ buffers/cache: 5.7G 2.1G
Swap: 2.0G 0B 2.0G
This other formula for totaling the memory roughly agrees:
# ps -e -orss=,args= | sort -b -k1,1n | awk '{total = total + $1}END{print total}'
503612
If the processes only total 500 MiB, where's the rest of the memory going?
I've got solution on this... so just wanna to update the same...
echo 2 > /proc/sys/vm/drop_caches
This resolved my issue. So I have added the same in my cron for every 5 mins on each of ubuntu server
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.
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
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.
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'
Building on gaoithe's answer, I attempted to make the memory units display in megabytes, and sorted by memory descending limited to 15 entries:
ps -e -orss=,args= |awk '{print $1 " " $2 }'| awk '{tot[$2]+=$1;count[$2]++} END {for (i in tot) {print tot[i],i,count[i]}}' | sort -n | tail -n 15 | sort -nr | awk '{ hr=$1/1024; printf("%13.2fM", hr); print "\t" $2 }'
588.03M /usr/sbin/apache2
275.64M /usr/sbin/mysqld
138.23M vim
97.04M -bash
40.96M ssh
34.28M tmux
17.48M /opt/digitalocean/bin/do-agent
13.42M /lib/systemd/systemd-journald
10.68M /lib/systemd/systemd
10.62M /usr/bin/redis-server
8.75M awk
7.89M sshd:
4.63M /usr/sbin/sshd
4.56M /lib/systemd/systemd-logind
4.01M /usr/sbin/rsyslogd
Here's an example alias to use it in a bash config file:
alias topmem="ps -e -orss=,args= |awk '{print \$1 \" \" \$2 }'| awk '{tot[\$2]+=\$1;count[\$2]++} END {for (i in tot) {print tot[i],i,count[i]}}' | sort -n | tail -n 15 | sort -nr | awk '{ hr=\$1/1024; printf(\"%13.2fM\", hr); print \"\t\" \$2 }'"
Then you can just type topmem on the command line.
How to total up used memory by process name:
Sometimes even looking at the biggest single processes there is still a lot of used memory unaccounted for. To check if there are a lot of the same smaller processes using the memory you can use a command like the following which uses awk to sum up the total memory used by processes of the same name:
ps -e -orss=,args= |awk '{print $1 " " $2 }'| awk '{tot[$2]+=$1;count[$2]++} END {for (i in tot) {print tot[i],i,count[i]}}' | sort -n
e.g. output
9344 docker 1
9948 nginx: 4
22500 /usr/sbin/NetworkManager 1
24704 sleep 69
26436 /usr/sbin/sshd 15
34828 -bash 19
39268 sshd: 10
58384 /bin/su 28
59876 /bin/ksh 29
73408 /usr/bin/python 2
78176 /usr/bin/dockerd 1
134396 /bin/sh 84
5407132 bin/naughty_small_proc 1432
28061916 /usr/local/jdk/bin/java 7
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
This very second in time
ps -U $(whoami) -eom pid,pmem,pcpu,comm | head -n4
Continuously updating
watch -n 1 'ps -U $(whoami) -eom pid,pmem,pcpu,comm | head -n4'
I also added a few goodies here you might appreciate (or you might ignore)
-n 1 watch and update every second
-U $(whoami) To show only your processes. $(some command) evaluates now
| head -n4 To only show the header and 3 processes at a time bc often you just need high usage line items
${1-4} says my first argument $1 I want to default to 4, unless I provide it
If you are using a mac you may need to install watch first
brew install watch
Alternatively you might use a function
psm(){
watch -n 1 "ps -eom pid,pmem,pcpu,comm | head -n ${1-4}"
# EXAMPLES:
# psm
# psm 10
}
You have this simple command:
$ free -h