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VE memory misconfigured / misreported [message #32626]

Wed, 20 August 2008 15:38

csigman
Messages: 7
Registered: February 2008

Junior Member

I've just created a VE running debian with apache, tomcat, mysql, and a custom java server app. On a regular, non-virtual server, the whole thing uses about a half gig of ram at most, however when I've got it running in the VE it is at least reported that it's using a whole lot more than that (about 2 gigs), even when idling, and thus I've tweaked my config to give it a lot more ram (at least inside the VE). Part of my issue stems from a gap in understanding as to what all of the memory configuration options actually do, but none the less, I'd really like to get a config, if possible, that shows a real and reliable amount of memory usage. Below is my current config:

KMEMSIZE="119516908:179249920"
LOCKEDPAGES="256:256"
PRIVVMPAGES="14939613:22406240"
SHMPAGES="31504:31504"
NUMPROC="240:240"
PHYSPAGES="0:2147483647"
VMGUARPAGES="415932:2147483647"
OOMGUARPAGES="831864:2147483647"
NUMTCPSOCK="360:360"
NUMFLOCK="188:206"
NUMPTY="16:16"
NUMSIGINFO="256:256"
TCPSNDBUF="1720320:2703360"
TCPRCVBUF="1720320:2703360"
OTHERSOCKBUF="1126080:2097152"
DGRAMRCVBUF="262144:262144"
NUMOTHERSOCK="360:360"
DCACHESIZE="3409920:3624960"
NUMFILE="9312:9312"
AVNUMPROC="180:180"
NUMIPTENT="128:128"

There's a few changes that are still in there from when I was trying to figure it all out, so just be aware if you see something crazy, that it might not be because I'm retarded with the config (even though I kind-of am).

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Re: VE memory misconfigured / misreported [message #32629 is a reply to message #32626]

Wed, 20 August 2008 22:44

piavlo
Messages: 159
Registered: January 2007

Senior Member

AFAIK you should be looking at oomguarpages
(oomguarpages parameter accounts the total amount of memory and swap space used by the processes of a particular container. The barrier of the oomguarpages parameter is the out-of-memory guarantee) in /proc/user_beancounters at "held" column to get initial estimation.
More details at http://wiki.openvz.org/UBC_systemwide_configuration
In particular at http://wiki.openvz.org/UBC_systemwide_configuration#Utilizat ion_2 if you are concerned with RAM utilization

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Re: VE memory misconfigured / misreported [message #32639 is a reply to message #32626]

Thu, 21 August 2008 14:26

csigman
Messages: 7
Registered: February 2008

Junior Member

So, I did a cat on user_beancounters, and I don't think that oomguarpages is really doing me much. Here's a before and after I adjusted using information from there:

Before:

       uid  resource           held    maxheld    barrier      limit    failcnt
      109:  kmemsize        5761486    7302244  119516908  179249920          0
            lockedpages           0          0        256        256          0
            privvmpages      455772     693191     504140     554554         51
            shmpages           1422       1438      31504      31504          0
            dummy                 0          0          0          0          0
            numproc             122        130        240        240          0
            physpages         48396      57609          0 2147483647          0
            vmguarpages           0          0     415932 2147483647          0
            oomguarpages      48396      57609     831864 2147483647          0
            numtcpsock           24         38        360        360          0
            numflock             12         62        188        206          0
            numpty                2          2         16         16          0
            numsiginfo            0         10        256        256          0
            tcpsndbuf        213792     411356    1720320    2703360          0
            tcprcvbuf        206684     799604    1720320    2703360          0
            othersockbuf      19980      30136    1126080    2097152          0
            dgramrcvbuf           0       8364     262144     262144          0
            numothersock         14         20        360        360          0
            dcachesize            0          0    3409920    3624960          0
            numfile            2503       2625       9312       9312          0
            dummy                 0          0          0          0          0
            dummy                 0          0          0          0          0
            dummy                 0          0          0          0          0
            numiptent            10         10        128        128          0

After:

       uid  resource           held    maxheld    barrier      limit    failcnt
      109:  kmemsize        4761437    5333291    9776841  119516908          0
            lockedpages           0          0        256        256          0
            privvmpages      487310     756408     919491   14939613          0
            shmpages            142        142      31504      31504          0
            dummy                 0          0          0          0          0
            numproc             108        126        240        240          0
            physpages         42568      55944          0 2147483647          0
            vmguarpages           0          0     415932 2147483647          0
            oomguarpages      42568      55944    2128630 2147483647          0
            numtcpsock           16         20        360        360          0
            numflock             12         13        188        206          0
            numpty                1          2         16         16          0
            numsiginfo            0          6        256        256          0
            tcpsndbuf        142080          0    1720320    2703360          0
            tcprcvbuf        214188     215384    1720320    2703360          0
            othersockbuf      17760      40548    1126080    2097152          0
            dgramrcvbuf           0       8364     262144     262144          0
            numothersock         12         23        360        360          0
            dcachesize            0          0    3409920    3624960          0
            numfile            2214       2525       9312       9312          0
            dummy                 0          0          0          0          0
            dummy                 0          0          0          0          0
            dummy                 0          0          0          0          0
            numiptent            10         10        128        128          0

I feel that the maxheld are misleading though, as htop shows max memory usage of almost 3gigs of the 3.5 allocated. The other very confusing thing is the resource usage on the host machine is definitely not nearly that much (1.5 gigs of ram used with 6 other ve's running)

[Updated on: Thu, 21 August 2008 14:35]

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Re: VE memory misconfigured / misreported [message #32643 is a reply to message #32639]

Thu, 21 August 2008 15:25

piavlo
Messages: 159
Registered: January 2007

Senior Member

So your VE current RAM usage is 171M since

(physpages*4096+kmemsize+allsocketbuf)/1024/1024=
=42568*4096+4761437+(142080+214188+17760+0)/1024/1024=
=179493993/1024/1024=171

Also since oomguarpages equals physpages (since no VE pages are swaped out by the kernel) the RAM+SWAP=RAM in your case.

Now total current allocated “virtual” (but not used) memory for VE is 1908MB

(privvmpages*4096+kmemsize+allsocketbuf)/1024/1024=
=487310*4096+4761437+(142080+214188+17760+0)/1024/1024=
2001157225/1024/1024=1908MB

This huge difference is since your VE apps ask for too much memory but don't actually use it. For example i took a look at my VE with nginx webserver and php-cgi and it's RAM usage is 55M while “virtual” memory is 92M. So look in tool like htop to find which of the apps is asking for too much memory but not using it.

It's all in http://wiki.openvz.org/UBC_systemwide_configuration

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Re: VE memory misconfigured / misreported [message #32647 is a reply to message #32643]

Thu, 21 August 2008 16:11

csigman
Messages: 7
Registered: February 2008

Junior Member

So, I guess the problem is that the swap and actual ram are shared from the ve's perspective, and java apps might allocate a huge amount of ram, but generally this is mostly in swap. I've toned down the memory usage of some of the java parts and that makes it so that it's using a lot less, but still not the most ideal setup. Luckily this is development, and production isn't in a VE.

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Re: VE memory misconfigured / misreported [message #32648 is a reply to message #32647]

Thu, 21 August 2008 16:36

piavlo
Messages: 159
Registered: January 2007

Senior Member

csigman wrote on Thu, 21 August 2008 19:11

So, I guess the problem is that the swap and actual ram are shared from the ve's perspective, and java apps might allocate a huge amount of ram, but generally this is mostly in swap.

Apps allocate vitrual memory which is neither in ram nor is swap. Only the real used memory is in ram or swap, and VE does not know where it is (it only sees "virtual" ram), but this does not matter.

Quote:

I've toned down the memory usage of some of the java parts and that makes it so that it's using a lot less, but still not the most ideal setup. Luckily this is development, and production isn't in a VE.

I think you are missing the point, the app virtual memory allocation does not depend if you are using OpenVZ or Vanilla kernel. Currently your VE is using 171M from RAM+SWAP
on HN or equally 171M of "virtual" ram on VE, so it is still safe for production.

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Re: VE memory misconfigured / misreported [message #32650 is a reply to message #32626]

Thu, 21 August 2008 22:02

csigman
Messages: 7
Registered: February 2008

Junior Member

Thanks for the explanation, that helps a lot!

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Re: VE memory misconfigured / misreported [message #33257 is a reply to message #32626]

Thu, 02 October 2008 11:42

mifritscher
Messages: 2
Registered: October 2008

Junior Member

The problem seems to be the shared memory: Each process using it has a big virtual memory, but this memory is only alloc one time. On openvz, this is counted shared_memory_size*accessing_processes.

This happens particulary with cachers like xcache,

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