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I am attempting to confirm swap usage on an OpenVZ vps. (I have had issues with badly configured swap files before)

To do so I am slowly filling the memory using code from this question How to test swap partition.

Then while running the code, monitoring memory and swap usage using top.

Whilst running, the swap usage does not change, instead the usage of the memeater code approaches real memory limits then stops.

Is this normal behaviour for the swap file in an OpenVZ setup?

Other useful info- - - -

swappiness = 60

# uname -a
Linux vps.server.com 5.4.0 #1 SMP Mon Mar 16 15:39:59 MSK 2020 x86_64 x86_64 x86_64 GNU/Linux

# cat /proc/user_beancounters
Version: 2.5
   uid  resource                     held              maxheld              barrier                limit              failcnt
 21423: kmemsize                 48521216            101617664  9223372036854775807  9223372036854775807                    0
        lockedpages                    93                  149  9223372036854775807  9223372036854775807                    0
        privvmpages                175203               477143  9223372036854775807  9223372036854775807                    0
        shmpages                      366                  368  9223372036854775807  9223372036854775807                    0
        dummy                           0                    0  9223372036854775807  9223372036854775807                    0
        numproc                        71                   71              4194304              4194304                    0
        physpages                  133247               262148               262144               262144                  381
        vmguarpages                     0                    0  9223372036854775807  9223372036854775807                    0
        oomguarpages               139011               276392                    0                    0                   14
        numtcpsock                      0                    0  9223372036854775807  9223372036854775807                    0
        numflock                        6                  104  9223372036854775807  9223372036854775807                    0
        numpty                          1                    4  9223372036854775807  9223372036854775807                    0
        numsiginfo                      0                   87  9223372036854775807  9223372036854775807                    0
        tcpsndbuf                       0                    0  9223372036854775807  9223372036854775807                    0
        tcprcvbuf                       0                    0  9223372036854775807  9223372036854775807                    0
        othersockbuf                    0                    0  9223372036854775807  9223372036854775807                    0
        dgramrcvbuf                     0                    0  9223372036854775807  9223372036854775807                    0
        numothersock                    0                    0  9223372036854775807  9223372036854775807                    0
        dcachesize               20279296             24981504  9223372036854775807  9223372036854775807                    0
        numfile                       860                 5590  9223372036854775807  9223372036854775807                    0
        dummy                           0                    0  9223372036854775807  9223372036854775807                    0
        dummy                           0                    0  9223372036854775807  9223372036854775807                    0
        dummy                           0                    0  9223372036854775807  9223372036854775807                    0
        numiptent                      44                   44  9223372036854775807  9223372036854775807                    0
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  • Would you happen to know which version of OpenVZ your VPS is on? Older versions of OpenVZ did not handle swap well. If you do not have access to the host, what is the output of uname -a in your VPS? Also, the output of cat /proc/user_beancounters could be useful. In the current version of OpenVZ, it is stated that if there is available memory on the host then swap within the VPS is not used (from the wiki). Oct 15, 2020 at 16:17
  • i've just added output to the OP
    – watermelon
    Oct 15, 2020 at 17:28
  • The output appears to be from a recent version of OpenVZ. If the free command is showing swap space, then your VPS should be able to use it. If you do not have access to the host, you may not be able to see swap space usage within your VPS unless the host is also out of memory. It is also possible for the host to configure your total available memory as RAM + swap space, or misconfigure your VPS so that it cannot make use of the swap space that is configured. Oct 15, 2020 at 19:24

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