Messages in this thread | | | Date | Tue, 9 Feb 2016 12:44:00 -0800 | From | Andi Kleen <> | Subject | Re: [PATCH] Optimize int_sqrt for small values for faster idle |
| |
On Sun, Feb 07, 2016 at 10:32:26PM +0100, Rasmus Villemoes wrote: > On Mon, Feb 01 2016, Andi Kleen <ak@linux.intel.com> wrote: > > > On Mon, Feb 01, 2016 at 10:25:17PM +0100, Rasmus Villemoes wrote: > >> On Thu, Jan 28 2016, Andi Kleen <andi@firstfloor.org> wrote: > >> > >> > From: Andi Kleen <ak@linux.intel.com> > >> > > >> > The menu cpuidle governor does at least two int_sqrt() each time > >> > we go into idle in get_typical_interval to compute stddev > >> > > >> > int_sqrts take 100-120 cycles each. Short idle latency is important > >> > for many workloads. > >> > > >> > >> If you want to optimize get_typical_interval(), why not just take the > >> square root out of the equation (literally)? > >> > >> Something like > > > > Looks good. Yes that's a better fix. > > > > Andi, did you have a way to measure the impact, and if so, could I get > you to run the numbers again with my patch?
I got the numbers from the 0day runs (AIM7 gets faster) In theory if you post the patch that should happen automatically (checking with Fengguang)
-Andi
-- ak@linux.intel.com -- Speaking for myself only
| |