From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752637AbaBNPai (ORCPT ); Fri, 14 Feb 2014 10:30:38 -0500 Received: from hofr.at ([212.69.189.236]:36035 "EHLO mail.hofr.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751374AbaBNPah (ORCPT ); Fri, 14 Feb 2014 10:30:37 -0500 Date: Fri, 14 Feb 2014 16:30:34 +0100 From: Nicholas Mc Guire To: Sebastian Andrzej Siewior Cc: linux-rt-users@vger.kernel.org, LKML , Steven Rostedt , Peter Zijlstra , Carsten Emde , Thomas Gleixner , Andreas Platschek Subject: Re: [PATCH RT 4/5] allow preemption in mem_cgroup_move_account_page_stat Message-ID: <20140214153034.GA4015@opentech.at> References: <20140210153933.GE20017@opentech.at> <20140214131705.GF28438@linutronix.de> <20140214131959.GG28438@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140214131959.GG28438@linutronix.de> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 14 Feb 2014, Sebastian Andrzej Siewior wrote: > * Sebastian Andrzej Siewior | 2014-02-14 14:17:05 [+0100]: > > >Now, that I look at it again. Isn't it more efficient to keep preemption > >disabled for this very short time instead instead of invoking > >migrate_disable() which includes preempt_disable()/enable() and a few > >more opcodes??? > >Therefore, I drop it again. > > I think doing the same for the 1/5 of this series since it also disables > migration for a handfull of asm opcodes. > yup - nice run in the wrong direction :) those short pushdowns make no sense - should have looked at that first... the execution length/complexity (notably worst case on migrate_enable()) is actually very high compared to a preempt_enable. thx! hofrat