On Thu, Jan 27, 2005 at 05:59:25PM +0800, Edward Yang wrote: > 4. It is hopelessly slower than FC1! I could run FC1 with only 128mb > memory and don't feel much sluggishness. I now run FC3 with 164mb > memory, but it is visibly slower than FC1! Application startup time is > almost unbearable. On *real* hardware, some things are slower, especially in RAM constrained situations; but many things are faster. Several changes could contribute to markedly slower performance in an emulator. You must understand that in an emulator, the guest scheduler and virtual memory system can have a complex interaction with the host scheduler and virtual memory system. The HZ setting in 2.6 defaults to 1000; it was 100 in 2.4. This can cause the host scheduler to see the guest as a CPU hog, resulting in longer latencies when you use it interactively -- it feels slower. There are patches working their way towards usability that would essentially eliminate unnecessary ticks of periodic clock, as this is desirable in virtual environment. But for starters, you might try setting HZ to 100, or tweaking some feature of VirtualPC. Another thing is that the kernel expects fast, uniform access to memory, unless it is using NUMA. The kernel has a tendency to touch memory pages all over the place, so if the entire emulation is not resident in memory on the host system, things slow down considerably; this effect is frequently seen in User-Mode Linux. Remember, access to your swap file is thousands of times slower than access to RAM! Until there is infrastructure in place for the guest OS to determine whether a page is in memory, and the guest OS uses it, this will continue to be a problem on memory-constrained systems. The "workaround" on Linux is for environments like User-Mode Linux to put their temporary files in ramfs or tmpfs. I don't know what, if any, tuning is possible with VirtualPC. As for your complaints of bloat and bugs, FC3 has its share of both, but in this community you report them and try to help fix them, rather than whining about it. You are empowered to do this -- that's the whole point, really! The upside for your investigative efforts is that, with the help of others, you can usually have a bug fix in days or weeks, and no proprietary OS, with at best quarterly releases, comes close to that, if they even bother to fix your bug at all. And if you prefer to be spoon fed, stick with a system other than Linux. Regards, Bill Rugolsky
