From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752987AbaHTMyf (ORCPT ); Wed, 20 Aug 2014 08:54:35 -0400 Received: from mail-we0-f173.google.com ([74.125.82.173]:36347 "EHLO mail-we0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752486AbaHTMyd (ORCPT ); Wed, 20 Aug 2014 08:54:33 -0400 Date: Wed, 20 Aug 2014 14:54:28 +0200 From: Ingo Molnar To: Kirill Tkhai Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Paul Turner , Oleg Nesterov , Steven Rostedt , Mike Galbraith , Kirill Tkhai , Tim Chen , Nicolas Pitre Subject: Re: [PATCH v5 0/5] sched: Add on_rq states and remove several double rq locks Message-ID: <20140820125428.GA6667@gmail.com> References: <1408528040.23412.86.camel@tkhai> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1408528040.23412.86.camel@tkhai> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Kirill Tkhai wrote: > v5: New names: TASK_ON_RQ_QUEUED, TASK_ON_RQ_MIGRATING, task_on_rq_migrating() > and task_on_rq_queued(). > > I've pulled the latest version from peterz/queue.git, and Peter's changes > are included. > > This series aims to get rid of some places where locks of two RQs are held > at the same time. > > Patch [1/5] is a preparation/cleanup. It replaces old (task_struct::on_rq == 1) > with new (task_struct::on_rq == TASK_ON_RQ_QUEUED) everywhere. No functional changes. > > Patch [2/5] is main in the series. It introduces new TASK_ON_RQ_MIGRATING state and > teaches scheduler to understand it (we need little changes in try_to_wake_up() > and task_rq_lock() family). This will be used in the following way: > > (we are changing task's rq) > > raw_spin_lock(&src_rq->lock); > > p = ...; /* Some src_rq task */ > > dequeue_task(src_rq, p, 0); > p->on_rq = TASK_ON_RQ_MIGRATING; > set_task_cpu(p, dst_cpu); > raw_spin_unlock(&src_rq->lock); > > /* > * Now p is dequeued, and both > * RQ locks are unlocked, but > * its on_rq is not zero. > * Nobody can manipulate p > * while it's migrating, > * even when spinlocks are > * unlocked. > */ > > raw_spin_lock(&dst_rq->lock); > p->on_rq = TASK_ON_RQ_QUEUED; > enqueue_task(dst_rq, p, 0); > raw_spin_unlock(&dst_rq->lock); > > Patches [3,4,5/5] remove double locks and use new TASK_ON_RQ_MIGRATING state. > They allow unlocked using of 3-4 function, which looks safe for me. > > The profit is that double_rq_lock() is not need in several places. We reduce > the total time when RQs are locked. > > --- > > Kirill Tkhai (5): > sched: Wrapper for checking task_struct::on_rq > sched: Teach scheduler to understand TASK_ON_RQ_MIGRATING state > sched: Remove double_rq_lock() from __migrate_task() > sched/fair: Remove double_lock_balance() from active_load_balance_cpu_stop() > sched/fair: Remove double_lock_balance() from load_balance() > > > kernel/sched/core.c | 113 +++++++++++++++------------ > kernel/sched/deadline.c | 15 ++-- > kernel/sched/fair.c | 195 ++++++++++++++++++++++++++++++++-------------- > kernel/sched/rt.c | 16 ++-- > kernel/sched/sched.h | 13 +++ > kernel/sched/stop_task.c | 2 > 6 files changed, 228 insertions(+), 126 deletions(-) > > -- > Signed-off-by: Kirill Tkhai Ok, looks good. I picked up this version, with a few minor tweaks and fixes to the changelogs. Thanks, Ingo