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utility atop shows:

ATOP - MyServer         2013/01/07  00:03:57               10 seconds elapsed
PRC | sys   2.18s | user   8.33s | #proc    141 | #zombie    0 | #exit      0 |
CPU | sys     21% | user    139% | irq       0% | idle    228% | wait     11% |
cpu | sys      5% | user     40% | irq       0% | idle     51% | cpu002 w  3% |
cpu | sys      5% | user     35% | irq       0% | idle     56% | cpu001 w  3% |
cpu | sys      7% | user     30% | irq       0% | idle     61% | cpu000 w  2% |
cpu | sys      4% | user     34% | irq       0% | idle     61% | cpu003 w  1% |
CPL | avg1   1.00 | avg5    1.12 | avg15   1.25 | csw   389208 | intr  223367 |
MEM | tot   23.6G | free  136.3M | cache   6.7G | buff   66.5M | slab  205.1M |
SWP | tot    0.0M | free    0.0M |              | vmcom  21.8G | vmlim  11.8G |
DSK |         sdc | busy     12% | read      70 | write    109 | avio    6 ms |
DSK |         sde | busy      4% | read      37 | write    131 | avio    2 ms |
DSK |         sdd | busy      3% | read      38 | write    144 | avio    1 ms |
NET | transport   | tcpi     160 | tcpo     171 | udpi       0 | udpo       0 |
NET | network     | ipi      188 | ipo      172 | ipfrw      0 | deliv    160 |
NET | vnet1    0% | pcki     510 | pcko     442 | si   60 Kbps | so   26 Kbps |
NET | eth0     0% | pcki     449 | pcko     527 | si   27 Kbps | so   65 Kbps |
NET | vnet0    0% | pcki       0 | pcko      44 | si    0 Kbps | so    3 Kbps |
NET | vnet7    0% | pcki       1 | pcko      44 | si    0 Kbps | so    3 Kbps |
NET | vnet2    0% | pcki       0 | pcko      43 | si    0 Kbps | so    3 Kbps |
NET | vnet3    0% | pcki       0 | pcko      43 | si    0 Kbps | so    3 Kbps |
NET | vnet6    0% | pcki       0 | pcko      43 | si    0 Kbps | so    3 Kbps |
NET | vnet5    0% | pcki       0 | pcko       5 | si    0 Kbps | so    0 Kbps |
NET | vnet4    0% | pcki       0 | pcko       5 | si    0 Kbps | so    0 Kbps |
NET | vnet8    0% | pcki       0 | pcko       5 | si    0 Kbps | so    0 Kbps |
NET | bond0  ---- | pcki     449 | pcko     527 | si   27 Kbps | so   65 Kbps |
NET | br0    ---- | pcki     157 | pcko     126 | si   12 Kbps | so   17 Kbps |
NET | lo     ---- | pcki      46 | pcko      46 | si    3 Kbps | so    3 Kbps |

My questions are following: 1)All is white, only line with SWP is RED. I have 24GB RAM and I don't use swap. How may I fix this? Is it big problem? I'm working on without problems, but who knows if is it bad or not?

2)What does vmcom and vmlim means?

CPU is Quad core. 3HDDs in RAID5. I have Debian Squeeze x64 and using KVM and MySQL.

Thank you for answer

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2 Answers 2

Answer to main query is further below - but first a warning regarding Mirra's suggestion:

Be careful with this:

In : /proc/sys/vm/overcommit_memory I try put there 2.

In that case, even when physical memory is available, all processes requesting memory from OS when vmcom greater than vmlim will receive errors (I`ve got a lot of errors and fails with basic system applications like compiz). And because of:

vmlim = SWAP_size + 0.5 * RAM_size.

where 0.5 (50%) is the default value for /proc/sys/vm/overcommit_ratio parameter you can easily get a lot of errors like me.


Answer to main question: it is better to revert changes in overcommit_memory parameter back to the default value (0 for me (Ubuntu 12.04 LTS), but can be 1 for other OS`es). According to the great article we can calculate memory actually used by processes:

MemoryUsed ~ tot - (cache + buff + free) ~ 23.6G - ( 6.7G + 0.067G + 0.136G) ~ 16.7G

So only 16.7G is actually used by processes (from 23.6G installed RAM) and red line in atop output may be ignored.

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up vote 0 down vote accepted

Problem can solve this:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/vm/overcommit-accounting;hb=HEAD

In : /proc/sys/vm/overcommit_memory I try put there 2.

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