"nf_conntrack: falling back to vmalloc" messages in /var/log/messages

"nf_conntrack: falling back to vmalloc" messages in /var/log/messages

Error: 

There are lot of messages  "kernel: nf_conntrack: falling back to vmalloc" in Messages file.
Oct  1 11:45:08 manastri.blogspot.com kernel: nf_conntrack: falling back to vmalloc.
Oct  1 12:45:22 manastri.blogspot.com kernel: nf_conntrack: falling back to vmalloc.
Oct  1 12:45:22 manastri.blogspot.com kernel: nf_conntrack: falling back to vmalloc.
Oct  1 13:45:16 manastri.blogspot.com kernel: nf_conntrack: falling back to vmalloc.
Oct  1 13:45:16 manastri.blogspot.com kernel: nf_conntrack: falling back to vmalloc.

Resolution:

Kernel uses two methods to allocate memory. kmalloc and vmalloc. Kmalloc allocates contiguous physical block. And it fails if contiguous block is not available and kernel falls back to vmalloc method. vmalloc means allocating memory that is only virtually contiguous. The reported error appears when memory is fragmented and the kernel is not able to get continuous free pages for allocation.
There are two possible solutions to this issue:

1. Increase vm.min_free_kbytes sysctl value.
Temporary Setting :

echo <value> > /proc/sys/vm/min_free_kbytes
sysctl -p

2. Rebooting the system would solve the memory fragmentation problem and the error would disappear.

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