Messages in this thread |  | | | Date | Mon, 16 Jul 2007 16:11:38 +0200 (CEST) | | From | Roman Zippel <> | | Subject | Re: [PATCH/RFC] msleep() with hrtimers |
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Hi,
On Sun, 15 Jul 2007, Jonathan Corbet wrote:
> The OLPC folks and I recently discovered something interesting: on a > HZ=100 system, a call to msleep(1) will delay for about 20ms. The > combination of jiffies timekeeping and rounding up means that the > minimum delay from msleep will be two jiffies, never less. That led to > multi-second delays in a driver which does a bunch of short msleep() > calls and, in response, a change to mdelay(), which will come back in > something closer to the requested time. > > Here's another approach: a reimplementation of msleep() and > msleep_interruptible() using hrtimers. On a system without real > hrtimers this code will at least drop down to single-jiffy delays much > of the time (though not deterministically so). On my x86_64 system with > Thomas's hrtimer/dyntick patch applied, msleep(1) gives almost exactly > what was asked for.
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.
bye, Roman - 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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