TCP stack throughput

[Valentin Micic]

> (*) I do not know if disabling HT makes a difference or not.

IMHO, it certainly should. Previous versions of RedHat had a very poor
support for mutliple CPUs, i.e. any given process would be bound to single
CPU, and hence, always executed on this particular processor. It is my
understanding that task scheduling did improve in AS 3.0, spreading process
execution accross all available processors. HT enabled CPU is seen as two
independent CPUs, and under such circumstances, a running away process shall
utilise 50% of each available processor. It makes sence, if you think about
it... any given process, at any given point shall be executed on one CPU.
Upon spending its slice, it will be rescheduled to another CPU, leaving the
previous alone. Thus, each processor is spending 50% of its time running,
and another 50% waiting... assuming that we have only one runaway.