On Thu, 2013-06-27 at 12:53 +0200, Peter Zijlstra wrote: > 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.
That cost sprang to mind when you mentioned that deadline needs hrtick. > 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. Could be worse, flaming marshmallows stick. -Mike -- 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/
