On Thu, Jun 27, 2013 at 12:43:09PM +0200, Peter Zijlstra wrote: > On Wed, Jun 26, 2013 at 10:46:33AM -0600, David Ahern wrote: > > On 6/26/13 1:05 AM, Peter Zijlstra wrote: > > >>What is the expectation that the feature provides? not a whole lot of > > >>documentation on it. I walked down the path wondering if it solved an odd > > >>problem we are seeing with the CFS in 2.6.27 kernel. > > > > > >Its supposed to use hrtimers for slice expiry instead of the regular tick. > > > > So theoretically CPU bound tasks would get preempted sooner? That was my > > guess/hope anyways. > > Doth the below worketh? >
Related to all this; the reason its not enabled by default is that mucking about with hrtimers all the while is god awful expensive. I've had ideas about making this a special purpose 'hard-coded' timer in the hrtimer guts that's only ever re-programmed when the new value is sooner. By making it a 'special' timer we can avoid the whole rb-tree song and dance; and by taking 'spurious' short interrupts we can avoid prodding the hardware too often. Then again; Thomas will likely throw frozen seafood my way for even proposing stuff like this and I'm not even sure that's going to be enough to make the cost acceptable. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
