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Confused with RAM usage
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Confused with RAM usage

I have CentOS 6.8 server with 12GB RAM and am confused with the RAM usage, it uses very minimal.

# free -m
             total       used       free     shared    buffers     cached
Mem:         12288      10978       1309        297          0      10723
-/+ buffers/cache:        254      12033
Swap:         2048       1559        488

If I am not mistaken, it's using only 254MB of ram, but using 3/4th of SWAP.
Just to make sure, I ran the munch script (http://www.linuxatemyram.com/play.html), and it allocated almost 12GB of ram.

Allocated 11809 MB
Allocated 11810 MB
Killed

The top command shows that it's using more than the 254MB.
I have vm.swappiness=0

 PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 1609 root      20   0  622m 146m  856 S  0.0  1.2   0:06.12 clamd
23888 root      20   0  244m  78m 3648 S  0.0  0.6   0:00.79 spamd child
15608 mysql     20   0 5794m  66m 4824 S  0.0  0.5   0:30.10 mysqld
 1628 root      20   0  231m  53m 5268 S  0.3  0.4   1:04.56 spamd
 1540 root      20   0 82352  18m  440 S  0.3  0.2   0:01.21 config
17544 nobody    20   0  139m  15m 2048 S  0.0  0.1   0:07.75 httpd
21618 nobody    20   0  139m  15m 1824 S  0.0  0.1   0:00.09 httpd
22526 nobody    20   0  139m  14m 1852 S  0.0  0.1   0:00.05 httpd
16015 nobody    20   0  139m  14m 1628 S  0.0  0.1   0:08.30 httpd
15982 nobody    20   0  139m  14m 1628 S  0.0  0.1   0:18.00 httpd
22552 nobody    20   0  139m  14m 1680 S  0.0  0.1   0:00.09 httpd
16048 nobody    20   0  139m  14m 1620 S  0.0  0.1   0:08.27 httpd
22648 nobody    20   0  139m  14m 1896 S  0.0  0.1   0:07.89 httpd
15974 nobody    20   0  139m  14m 1564 S  0.0  0.1   0:09.75 httpd
17844 nobody    20   0  139m  14m 1660 S  0.0  0.1   0:08.89 httpd
16062 nobody    20   0  139m  13m 1748 S  0.0  0.1   0:10.43 httpd
22557 nobody    20   0  139m  13m 1716 S  0.0  0.1   0:00.04 httpd
21920 nobody    20   0  139m  13m 1748 S  0.0  0.1   0:00.10 httpd
15735 nobody    20   0  139m  13m 1380 S  0.0  0.1   0:00.35 httpd
22514 nobody    20   0  139m  13m 1772 S  0.0  0.1   0:00.07 httpd
16011 nobody    20   0  139m  12m 1556 S  0.0  0.1   0:10.35 httpd
15927 nobody    20   0  139m  12m 1552 S  0.0  0.1   0:00.26 httpd
23913 cpanelro  20   0  103m  12m 2988 S  0.0  0.1   0:00.01 webmaild - serv
22520 nobody    20   0  139m  11m 1656 S  0.0  0.1   0:00.03 httpd
15890 nobody    20   0  139m  11m 1540 S  0.0  0.1   0:21.77 httpd
16052 nobody    20   0  139m  10m  116 S  0.0  0.1   0:07.49 httpd
17281 nobody    20   0  139m  10m  184 D 17.0  0.1   0:12.72 httpd
21886 nobody    20   0  139m  10m  112 S  0.0  0.1   0:00.05 httpd
15984 nobody    20   0  139m  10m  112 S  0.0  0.1   0:07.68 httpd
17519 nobody    20   0  139m  10m 1588 S  0.0  0.1   0:00.37 httpd
15724 nobody    20   0  139m  10m  112 S  0.0  0.1   0:09.72 httpd
22519 nobody    20   0  139m  10m  112 S  0.0  0.1   0:00.03 httpd
15728 nobody    20   0  139m   9m  148 S  0.0  0.1   0:00.31 httpd
21601 nobody    20   0  139m 9.9m  112 S  0.0  0.1   0:09.83 httpd
22875 nobody    20   0  139m 9.9m  236 D 16.6  0.1   0:05.36 httpd
15825 nobody    20   0  139m 9.9m  112 S  0.0  0.1   0:10.98 httpd
22741 nobody    20   0  139m 9.9m  232 D 16.0  0.1   0:05.34 httpd
17618 nobody    20   0  139m 9.8m  176 D 17.3  0.1   0:33.77 httpd
16010 nobody    20   0  139m 9.8m  176 D 16.3  0.1   0:15.74 httpd
15742 nobody    20   0  139m 9.8m  148 S  0.0  0.1   0:07.50 httpd
21598 nobody    20   0  139m 9972  148 S  0.0  0.1   0:00.09 httpd
22783 nobody    20   0  139m 9968  116 S  0.0  0.1   0:00.09 httpd
17845 nobody    20   0  139m 9960  116 S  0.0  0.1   0:07.87 httpd
15976 nobody    20   0  139m 9940  112 S  0.0  0.1   0:10.70 httpd
22773 nobody    20   0  139m 9932  116 S  0.0  0.1   0:00.06 httpd
22774 nobody    20   0  139m 9932  120 S  0.0  0.1   0:07.65 httpd
22780 nobody    20   0  139m 9928  116 S  0.0  0.1   0:00.06 httpd
22844 nobody    20   0  139m 9928  116 S  0.0  0.1   0:00.07 httpd
17295 nobody    20   0  139m 9924  112 S  0.0  0.1   0:08.82 httpd
17590 nobody    20   0  139m 9924  116 S  0.0  0.1   0:15.25 httpd
18380 nobody    20   0  139m 9924  152 S  0.0  0.1   0:00.27 httpd
22571 nobody    20   0  139m 9924  112 S  0.0  0.1   0:07.81 httpd

Do you think there's some stuff wrong with my server? Why is it using swap when there's 12GB of free RAM.

Comments

  • IkoulaIkoula Member, Host Rep

    Hello,

    To me and according to your #free command near 11 Gb ram is used.

  • sleddogsleddog Member
    edited October 2016

    Drukpa said: If I am not mistaken, it's using only 254MB of ram, but using 3/4th of SWAP. Just to make sure, I ran the munch script (http://www.linuxatemyram.com/play.html), and it allocated almost 12GB of ram.

    Did you disable swap before running that munch test (as instructed)? Were you using swap before running it, or only after?

    Drukpa said: The top command shows that it's using more than the 254MB.

    I don't see that as you didn't post the header info from top. You can't simply add up the columns and get the amount of ram used. Many of those items are threads and reflect the same ram usage.

    Drukpa said: Do you think there's some stuff wrong with my server? Why is it using swap when there's 12GB of free RAM.

    Either you had swap enabled and ran munch, or some of your processes are using large amounts of ram for a short time, causing your system to swap, and then settle down.

    1. Reboot to clear thing up.
    2. Don't run that munch script. It just confuses the situation.
    3. Monitor your memory usage.
    4. Adjust daemons to work within your available ram, e.g. limit what spamd, clamd, httpd, mysql, etc. can consume.
  • raindog308raindog308 Administrator, Veteran

    Ikoula said: To me and according to your #free command near 11 Gb ram is used.

    Nope: http://www.linuxatemyram.com

  • exception0x876exception0x876 Member, Host Rep, LIR
    edited October 2016

    you may need to adjust /proc/sys/vm/swappiness if you don't want the kernel to swap the less used memory in a favour of system page cache.

  • @Ikoula said:
    Hello,

    To me and according to your #free command near 11 Gb ram is used.

    As a provider you should know how to read free -m ....

    Thanked by 2seriesn Quinten
  • Just Linux being Linux. Nothing to sweat about it. You are way way under your limit.

  • IkoulaIkoula Member, Host Rep

    @raindog308 @ATHK technically what i said is not false 11 Gb is used but is also available for applications.
    Where i am wrong in the end is more because i did not answer to the OP questioning :/

  • edited October 2016

    10978MB used but 10723MB are for caching so in reality just 254MB used.

    Drukpa said: # free -m

    total used free shared buffers cached
    Mem: 12288 10978 1309 297 0 10723
    -/+ buffers/cache: 254 12033

    And unless you set swap = 0 Linux won't use swap, then even with swappiness=0 it will still try to allocate disk swap, normal behaviour.

  • 10978 Ram is used

  • @AlphaNinevps_com said:
    10978 Ram is used

    No 10978 is cached the ops total memory usage is read from
    -/+ buffers/cache: 254 12033

    Which will indicate that the os is currently using 254 mb of ram and there is 12033 'free'

    Op I'd recommend installing htop as it will give you a clear idea of how much memory you are using but you are correct in thinking you are using 254 mb don't worry some much about virtual memory.

  • @DrFallen said:

    @AlphaNinevps_com said:
    10978 Ram is used

    No 10978 is cached the ops total memory usage is read from
    -/+ buffers/cache: 254 12033

    Which will indicate that the os is currently using 254 mb of ram and there is 12033 'free'

    Op I'd recommend installing htop as it will give you a clear idea of how much memory you are using but you are correct in thinking you are using 254 mb don't worry some much about virtual memory.

    Try reboot it once.

  • @AlphaNinevps_com said:

    @DrFallen said:

    @AlphaNinevps_com said:
    10978 Ram is used

    No 10978 is cached the ops total memory usage is read from
    -/+ buffers/cache: 254 12033

    Which will indicate that the os is currently using 254 mb of ram and there is 12033 'free'

    Op I'd recommend installing htop as it will give you a clear idea of how much memory you are using but you are correct in thinking you are using 254 mb don't worry some much about virtual memory.

    Try reboot it once.

    For what effect?

    Thanked by 1Amitz
  • yomeroyomero Member
    edited October 2016
    • You ran the script with swap enabled.

    • Linux moved other processes stuff to swap because you were asking for more ram.

    • The script was killed after linux didn't found a way to give you more ram.

    • Linux won't move back that processes to ram, until you need their memory pages, because is IO expensive to do that.

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