tigervnc/tests/results/multicore

This directory contains the evaluation of the multi-core implementation
in the decoder. The baseline is the performance before the addition of
the DecodeManager class.

Tests were performed on the following systems:

 - eLux RP Atom N270 1.6 GHz
 - Lubuntu 13.10 i.MX6 Quad 1.2 GHz
 - Fedora 22 i7-3770 3.4 GHz
 - Windows Vista Core 2 Duo E7400 2.8 GHz
 - Windows 10 i3-4170 3.7 GHz
 - OS X 10.6 Core 2 Duo 2.53 GHz
 - OS X 10.11 i5 2.3 GHz

The systems were tested with:

 a) The old, baseline code
 b) The new code with all CPUs enabled
 c) The new code with only one CPU enabled

The test itself consists of running decperf on the test files from the
TurboVNC project. Rate of decoding is then compared to the baseline.
Note that the CPU time is divided by core usage in the multi CPU cases
in order to derive total decoding time. This method is sensitive to
other load on the system.

On average, there is no regression in performance for single CPU
systems. This however relies on the addition of the single CPU shortcut
in DecodeManager. Without that the performance sees a 10% lower rate.

Dual CPU systems see between 20% and 50% increase, and the quad core
systems between 75% and 125% on average. OS X is an outlier though in
that it gets a mere 32% increase on average. It is unknown why at this
point and tracing doesn't reveal anything obvious. It may be because it
is not a true quad core system, but rather uses HyperThreading.

So in summary, the new code can do a noticeable improvement on decoding
time. However it does so at a cost of efficiency. Four times the CPUs
only gives you about twice the performance. More improvements may be
possible.