Messages in this thread | | | Date | Mon, 16 Jul 2007 12:48:44 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH/RFC] msleep() with hrtimers |
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* Jonathan Corbet <corbet@lwn.net> 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. > > jon > > Use hrtimers for msleep() and msleep_interruptible() > > Signed-off-by: Jonathan Corbet <corbet@lwn.net>
i certainly like this - an msleep() is like mdelay(), so there are real delays (and not timeouts) involved, so converting to hrtimers is the right thing to do from a conceptual POV too.
Acked-by: Ingo Molnar <mingo@elte.hu>
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