Why are all applications unloaded to swap when memory is empty (VPS OpenVZ)?

Question

linux

VPS on OpenVZ has 8 GB RAM and 4 GB swap. Debian 7 x64 system.
Faced such a problem: after restoring the database from a backup (.sql 14 GB), all applications are forced out into swap, and the memory is completely allocated for disk cache. Can you please tell me why this is happening and how to deal with it?
[email protected]~# htop (dropped to 0, 3MB on screenshot)
[email protected]~# cat /proc/meminfo
Script northernmost.org/blog/find-out-what-is-using-your-swap

Answer 1

Do echo 3 > /proc/sys/vm/drop_caches
Better directly on the host.
If there is a swap on the hardware, then a part of your "virtual" swap will go to disk (vswap keeps swap in memory only as long as there is memory in principle).
It can be just a traditional glitch with the calculation of occupied memory in openvz, or it can be quite a glitch with memory allocation.

Answer 2

It can be seen on the top that all the memory is used. Why be surprised then?

Answer 3

Actually, this process can be regulated through overcommit:
catap.ru/blog/2009/05/05/about-memory-overcommit-memory