Quoting Ed Russell <[EMAIL PROTECTED]>, on Sat 26 Apr 2008 07:09:57 AM PDT:
> Jim, > > When I'm not getting QSK and my CPU is at 8%, I'm wondering where the > bottleneck is. 250ms latency is a real long time in the cpu universe. Indeed.. 250ms is an eternity.. Are you using process explorer or task manager to look at the 8%.. Turns out that there are things that can be going on in Windows that consume CPU resources that don't necessarily show up in the CPU utilization. A notorious one for me at work is network file accesses. Under some poorly understood set of conditions (meaning I haven't spent much time figuring it out), a task on my computer (email, word, etc.) slows to a crawl. I've figured out so far that the task is waiting for some API to return, typically a "file system directory" sort of call.. and it's waiting for the network to come back and tell it that it's failed or worked. This can happen, even if the network is up and running, and all the network file services are fine. I think it loses track of whether it's gotten the acknowledge back or something. Either that, or there's something in the internals of Windows or a poorly behaved device driver/service from a 3rd party, that makes the unwarranted assumption that all file accesses are to a local drive. Adobe license manager service also seems to cause troubles... Acrobat appears to hang.. There were some interactions with the OpenAFS and Transarc AFS clients at one time too. Or, maybe it's some sort of kernel scheduling artifact..a high priority thread grabs the kernel, and doesn't release it when it should. Even robust real time operating systems can have these sorts of things, and Windows, in general, isn't really designed for real time applications (at least not at the millisecond scale). If you need honest streaming real-time performance (e.g. streaming video or audio) from windows, it's a fair amount of down and dirty Windows API programming to fit yourself into their scheduling model, account for all the things that hiccup, etc. I don't know that PowerSDR has gone to that much trouble (or, more precisely, that the pthreads implementers have done this). So, the take home message is that it's not necessarily a CPU loading issue. The runtime environment is quite complex, and not everybody follows all the rules or is thoroughly debugged. One of the theoretical advantages of Vista (not yet fully realized) is that it has a much more robust model for real time and streaming.. because it's needed for providing entertainment services (along with digital rights management). If someone has paid $10 for a payperview movie or $50 for pay-per-view sporting events on their Vista box, they're going to be pretty cranky if it hiccups all the time. Jim, W6RMK _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/
