hyperthreading and the cpu usage

http://exadata-dba.blogspot.com/2014/01/system-performance-utilities-show-wrong.html

For CPU utilization less than 50%, multiply by 1.7.

∙ For CPU utilization over 50%, assume 85% plus (util-50%)* 0.3.

Here is a table that summarizes the effect: Measured Utilization	Actual Utilization
10%	17%
20%	34%
30%	51%
40%	68%
50%	85%
60%	88%
70%	91%
80%	94%
90%	97%
100%	100%

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This information is applicable to all x86 abd x86-64 servers with HyperThreading enabled.

Enabling HT causes system statistics tools - vmstat, sar - show incorrect CPU load,
and Oracle performance tools - AWR, ASH - also show and store incorrect CPU load statistics.