By using one thread per logical CPU thread, we seemed to completely saturate
the CPU which would kill the performance of the main/GUI thread (despite the
other threads being low priority). We now use half of the logical threads, which
still sees good CPU usage and minimal performance impact while allowing the
main thread to respond to user actions.
We use Qt's built in zlib compression on the fastest setting (it was found that
higher compression took 5x as long with a negligible decrease in size). This
helps keep disk cache sizes low.
itsmattkc