[Users] Problems with plesk + openvz

[Joan]

Good morning

I've got a plesk installation on a openvz as the single VeID in the
machine (vzsplit -n 1).
The box has 3.5 Gb of memory, and is a 2000GHz Dual Core.
For around of 200 domains the machine should be fine i guess.
But, all the time we are being left with no memory.
Almost every day privvmpages break the counter in user_beancounters.
And after restarting apache2 everything goes fine.

It's a problem with plesk eating all the memory, apache2-mpm-prefork,
openvz memory management or what?

Thanks in advance