On Sat, Jan 29, 2005 at 02:02:57PM -0500, James Armstrong wrote: > Brad Templeton wrote: > > I am getting the following while watching HD 1080i on CBS: 38% User, > 2.2% System and 56.1% Idle > > .3% cpu usage for mythfrontend > mythbackend on another computer > 12% for X > .3% for lirc_dev > <1% for top and others > > This is on a 3gig Pentium4 HT with 8meg cache. 1gig memory, NVidia 5200.
Yes, as noted, the HT P4s reprot very good numbers, though there's been some recent debate off list about whether they are true or not, I'm still researching it. Hyperthreading, for those who don't know, means the P4 pretends to be a dual-processor system by duplicating the registers and various elements of the ALU, but not the entire CPU by any stretch. This means that for certain algorithms, ones that are ALU bound rather than memory bound, and which are multi-threaded, you can see a real improvement. There is speculation that mpeg encode and decode are in this category. But it makes it hard to figure out how "idle" the processor is because sometimes one of the units may be "idle" but in fact it could not really do anything. So we need to do some tests as follows: a) Try mpeg decode on a P4 with the non-SMP kernel. b) Get a benchmark program which can be run niced, to try to figure out how much spare capacity each different test system has while playing 1080i. Note that this just tells us how much spare capacity there is to run the benchmark program. What we care about is the following though: a) Is there enough spare capacity so that when minor system tasks take place, they don't make video skip. b) Is there enough capacity to do that if you also throw in a niced thread to do commercial elimination or transcode? c) Do we have enough capacity to handle "peak" decoding load, since that varies with scene complexity. And also d) What's the cheapest processor we can get away with and still play skip-free 1080i and 720p? xvmc of course can also change this equation a lot. On my P4, for example, playing 1080i in mplayer with xvmc, I have seen idle times over 80% which sounds good and implies one could get away with something much less in this environment.
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