From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Subject: Re: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex Date: Wed, 23 Jul 2014 09:25:46 +0200 Message-ID: <1406100346.5076.98.camel@marge.simpson.net> References: <1405956271-34339-1-git-send-email-Waiman.Long@hp.com> <8761iq3bp3.fsf@tassilo.jf.intel.com> <1406091303.5076.33.camel@marge.simpson.net> <20140723065736.GM3935@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140723065736.GM3935@laptop> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Peter Zijlstra Cc: Andi Kleen , Waiman Long , Thomas Gleixner , Ingo Molnar , Darren Hart , Davidlohr Bueso , Heiko Carstens , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jason Low , Scott J Norton List-Id: linux-api@vger.kernel.org On Wed, 2014-07-23 at 08:57 +0200, Peter Zijlstra wrote: > On Wed, Jul 23, 2014 at 06:55:03AM +0200, Mike Galbraith wrote: > > On Mon, 2014-07-21 at 09:42 -0700, Andi Kleen wrote: > > > > > FWIW the main problem is currently that switch-through-idle is so > > > slow. I think improving that would give a boost to far more > > > situations. > > > > Two high frequency idle enter/exit suckage spots: > > > > 1) nohz (tick) - it's expensive to start/stop tick on every micro-idle, > > throttle it or something. > > Yeah, so the idea was to use the cpuidle idle guestimator to control > this, and now that we've moved it somewhat closer to the scheduler that > might become possible. > > > 2) ondemand governor - tweak silly default settings to reflect the > > reality that we routinely schedule communicating threads cross core. > > Yeah, so the plan is to shoot cpufreq in the head and base the > replacement on smp aware metrics ;-) Its on a todo list somewhere.. It never ceases to amaze me that people aren't screaming bloody murder about those two spots. Watching performance of lightly loaded boxen is enough to make a grown man cry. SUSE (and I in all of my many regression testing trees) puts tourniquets on both of these blood spurting gashes, laptops be damned. I also resurrect mwait_idle(), as while you may consider it obsolete, I still love my lovely little Q6600 box (power sucking pig) dearly :) -Mike