Hey, Roman, > One possible problem here is that setting up that timer can be > considerably more expensive, for a relative timer you have to read the > current time, which can be quite expensive (e.g. your machine now uses the > PIT timer, because TSC was deemed unstable).
That's a possibility, I admit I haven't benchmarked it. I will say that I don't think it will be enough to matter - msleep() is not a hot-path sort of function. Once the system is up and running it almost never gets called at all - at least, on my setup. > One question here would be, is it really a problem to sleep a little more? "A little more" is a bit different than "twenty times as long as you asked for." That "little bit more" added up to a few seconds when programming a device which needs a brief delay after tweaking each of almost 200 registers. > BTW there is another thing to consider. If you already run with hrtimer/ > dyntick, there is not much reason to keep HZ at 100, so you could just > increase HZ to get the same effect. Except that then, with the current implementation, you're paying for the higher HZ whenever the CPU is busy. I bet that doesn't take long to overwhelm any added overhead in the hrtimer msleep(). In the end, I did this because I thought msleep() should do what it claims to do, because I thought that getting a known-to-expire timeout off the timer wheel made sense, and to make a tiny baby step in the direction of reducing the use of jiffies in the core code. jon - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
