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Nigel Gamble wrote: > > On Thu, 10 Jan 2002, Alan Cox wrote: > > The fun below 1mS comes from > > > > 1. APM bios calls where the bios decides to take >1mS to have > > a chat with your batteries > > 2. Video cards pulling borderline legal PCI tricks to get > > better benchmarketing by stalling the entire bus > > Don't forget the embedded space, where the hardware vendor can ensure > that their hardware is well-behaved. Even on a PC, it is possible for > someone who cares about realtime to spec a reasonable system. > > On good hardware, we can easily do much better than 1ms latency with a > preemptible kernel and a spinlock cleanup. I don't think the > limitations of some PC hardware should limit our goals for Linux. > On 700MHz x86 running Cerberus we can do 50 microseconds average and 1300 microseconds worst-case today. Below 1000 uSec, the required changes get exponentially larger and more complex. I doubt that it's sane to try to go below a millisecond on a desktop-class machine with desktop-class workload, disk, memory and swap capacities. On a more constrained system, which is what I expect you're referring to, 250 microseconds should be achievable. Whether or not that is achieved via preemptability is pretty irrelevant. - - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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