Page cache isolation

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Warning.svg Warning: This article describes legacy version of OpenVZ (version 6).

This feature is absent in OpenVZ 7, similar feature in OpenVZ 7 is called tcache.

This page describes a new strict page cache isolation feature, which appeared in the kernel 2.6.32-042stab068.8.

The feature disables bouncing page cache pages between host and containers on physpages shortage in container. The internal reclaimer will drop cached data if container exceeded its physpages limit and pagecache isolation is turned on.

Current state can be obtained by reading the /proc/bc/<id>/debug:pagecache_isolation file. It is disabled by default.

The following sysctls are available:

  • ubc.pagecache_isolation = 0|1
To turn on or off isolation for all containers
  • ubc.pagecache_isolation_on = <id>
To turn on for container <id> (write only)
  • ubc.pagecache_isolation_off = <id>
To turn off for container <id> (write only)
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