What determines memory speed of OpenVZ container?
sysbench --test=memory --memory-block-size=1M --memory-total-size=1G run on several OpenVZ powered VPSs from different providers and observed memory bandwidth measured from 2920.06 MB/sec to 11980.72 MB/sec.
I've made several observations in different daytime. Rounded numbers below are in GB/s:
VPS1 | 2.9 - 3.6 VPS2 | 3.9 - 4.6 VPS3 | 7.0 - 7.4 VPS4 | 11.9 - 12.0
All VPSs are with 32bit OS, except VPS3.
For reference I've benchmarked my old cheap laptop with DDR2 inside and got 4GB/s.
My guess is that memory bandwidth in container = practical memory bandwidth of hardware * available CPU share. Then assuming DDR3 on most nodes with, say, 12800MB/s throughput we can derive that VPS1 allows to use no more than ~28% of host CPU (3.6/12.8), VPS2 ~36%, etc. Am I right?