Tell me what process uses all of the ram?
Before actually asking, just to be clear: yes, I know about disk cache, and no, it is not my case :) Sorry, for this preamble :)
I'm using centos 5. Every application in the system swaps heavily and the system is very slow When I do
free -m , here is what I got.
total used free shared buffers cached Mem: 3952 3929 22 0 1 18 -/+ buffers/cache: 3909 42 Swap: 16383 46 16337
So i actually have only 42 mb to use As far as I understand,
-/+ buffers/cache actually doesn't count the disk cache, so I indeed only have 42 Mb, right? I thought, i might be wrong, so i tried to switch off the disk caching and it had no effect - the picture remained the same.
So, I decided to find out who is using all my RAM, and I used
top for that. It appears that no program is using my ram The only process in my top is MySQL, but it is using 0.1% of RAM and 400Mb of swap. Same picture when I try to run other services or applications - all go in swap,
top shows that MEM is not used (0.1% maximum for any process).
top - 15:09:00 up 2:09, 2 users, load average: 0.02, 0.16, 0.11 Tasks: 112 total, 1 running, 111 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4046868k total, 4001368k used, 45500k free, 748k buffers Swap: 16777208k total, 68840k used, 16708368k free, 16632k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ SWAP COMMAND 3214 ntp 15 0 23412 5044 3916 S 0.0 0.1 0:00.00 17m ntpd 2319 root 5 -10 12648 4460 3184 S 0.0 0.1 0:00.00 8188 iscsid 2168 root RT 0 22120 3692 2848 S 0.0 0.1 0:00.00 17m multipathd 5113 mysql 18 0 474m 2356 856 S 0.0 0.1 0:00.11 472m mysqld 4106 root 34 19 251m 1944 1360 S 0.0 0.0 0:00.11 249m yum-updatesd 4109 root 15 0 90152 1904 1772 S 0.0 0.0 0:00.18 86m sshd 5175 root 15 0 90156 1896 1772 S 0.0 0.0 0:00.02 86m sshd
Restart doesn't help, and, by they way is very slow, which I wouldn't normally expect on this machine (4 cores, 4Gb RAM, RAID1).
I'm pretty sure this is not a disk cache which uses the ram because normally it should have been reduced and let other processes use ram rather than swap
Why do some processes use memory so heavily?
On Linux in the
top process you can press
< key to shift the output display sort left. By default it is sorted by the
%CPU so if you press the key 4 times you will sort it by
VIRT which is virtual memory size giving you your answer.
You can find another way to do it
ps -e -o pid,vsz,comm= | sort -n -k 2
should give you and output sorted by processes virtual size.
This is the long version
ps --everyone --format=pid,vsz,comm= | sort --numeric-sort --key=2