May be you hit memory shortage in a particular NUMA node only, for example.

# numactl --hardware
# numastat -m


Or go hard way - trace kernel where exactly do we get -ENOMEM:

trace the kernel function cgroup_mkdir() using /sys/kernel/debug/tracing/
with function_graph tracer.


https://lwn.net/Articles/370423/

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team

On 01/28/2021 12:43 PM, Joe Dougherty wrote:
I checked that, doesn't appear to be the case.

*# pwd*
*/sys/fs/cgroup/memory*
*# cat *limit_in_bytes*
*9223372036854771712*
*9223372036854767616*
*2251799813685247*
*2251799813685247*
*9223372036854771712*
*9223372036854771712*
*9223372036854771712*
*# cat *failcnt*
*0*
*0*
*0*
*0*
*0*

# pwd
/sys/fs/cgroup/memory/machine.slice
*# cat *limit_in_bytes*
*9223372036854771712*
*9223372036854767616*
*9223372036854771712*
*9223372036854771712*
*9223372036854771712*
*9223372036854771712*
*9223372036854771712*
*# cat *failcnt*
*0*
*0*
*0*
*0*
*0*



On Thu, Jan 28, 2021 at 2:47 AM Konstantin Khorenko <[email protected] 
<mailto:[email protected]>> wrote:

    Hi Joe,

    i'd suggest to check memory limits for root and "machine.slice" memory 
cgroups

    /sys/fs/cgroup/memory/*limit_in_bytes
    /sys/fs/cgroup/memory/machine.slice/*limit_in_bytes

    All of them should be unlimited.

    If not - search who limit them.

    --
    Best regards,

    Konstantin Khorenko,
    Virtuozzo Linux Kernel Team

    On 01/27/2021 10:28 PM, Joe Dougherty wrote:
    I'm running into an issue on only 1 of my OpenVZ 7 nodes where it's unable to create 
a directory on /sys/fs/cgroup/memory/machine.slice due to "Cannot allocate 
memory"
    whenever I try to start a new container or restart and existing one. I've 
been trying to research this but I'm unable to find any concrete info on what 
could cause this. It
    appears to be memory related because sometimes if I issue "echo 1 
/proc/sys/vm/drop_caches" it allows me to start a container (this only works 
sometimes) but my RAM usage
    is extremely low with no swapping (swappiness even set to 0 for testing). 
Thank you in advance for your help.


    Example:
    *# vzctl start 9499*
    *Starting Container ...*
    *Mount image: /vz/private/9499/root.hdd*
    *Container is mounted*
    *Can't create directory /sys/fs/cgroup/memory/machine.slice/9499: Cannot 
allocate memory*
    *Unmount image: /vz/private/9499/root.hdd (190)*
    *Container is unmounted*
    *Failed to start the Container*


    Node Info:
    *Uptime:      10 days*
    *OS:          Virtuozzo 7.0.15*
    *Kernel: 3.10.0-1127.18.2.vz7.163.46 GNU/Linux*
    *System Load: 3.1*
    */vz Usage:   56% of 37T*
    *Swap Usage:  0%*
    *RAM Free:    84% of 94.2GB*
    *
    *
    *# free -m*
    *                    total        used       free            shared   
buff/cache  available*
    *Mem:          96502       14259  49940         413         32303  80990*
    *Swap:         32767       93  32674*


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--
*/-Joe Dougherty/*
*/Chief Operating Officer/*
/***Secure Dragon LLC */
*/www.SecureDragon.net <http://www.SecureDragon.net>/*


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