From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Subject: Re: [Bug #12208] uml is very slow on 2.6.28 host Date: Tue, 16 Dec 2008 04:25:27 +0100 Message-ID: <1229397927.5296.48.camel@marge.simson.net> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Miklos Szeredi Cc: rjw-KKrjLPT3xs0@public.gmane.org, a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Tue, 2008-12-16 at 01:49 +0100, Miklos Szeredi wrote: > On Sat, 13 Dec 2008, Rafael J. Wysocki wrote: > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12208 > > Subject : uml is very slow on 2.6.28 host > > Submitter : Miklos Szeredi > > Date : 2008-12-12 9:35 (2 days old) > > References : http://marc.info/?l=linux-kernel&m=122907463518593&w=4 > > I did a bisection, and this is the commit which is responsible: > > commit 464b75273f64be7c81fee975bd6ca9593df3427b > Author: Peter Zijlstra > Date: Fri Oct 24 11:06:15 2008 +0200 > > sched: re-instate vruntime based wakeup preemption > > The advantage is that vruntime based wakeup preemption has a better > conceptual model. Here wakeup_gran = 0 means: preempt when 'fair'. > Therefore wakeup_gran is the granularity of unfairness we allow in order > to make progress. > > Signed-off-by: Peter Zijlstra > Acked-by: Mike Galbraith > Signed-off-by: Ingo Molnar If that commit is responsible, then it should also be very slow in pre 28 kernels, where the same exists. Hm, there's another possibility. Can you try echo NO_LAST_BUDDY > /sys/kernel/debug/sched_features? -Mike