From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265918AbUAKQ50 (ORCPT ); Sun, 11 Jan 2004 11:57:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265919AbUAKQ50 (ORCPT ); Sun, 11 Jan 2004 11:57:26 -0500 Received: from x35.xmailserver.org ([69.30.125.51]:64673 "EHLO x35.xmailserver.org") by vger.kernel.org with ESMTP id S265918AbUAKQ5Y (ORCPT ); Sun, 11 Jan 2004 11:57:24 -0500 X-AuthUser: davidel@xmailserver.org Date: Sun, 11 Jan 2004 08:57:28 -0800 (PST) From: Davide Libenzi X-X-Sender: davide@bigblue.dev.mdolabs.com To: Der Herr Hofrat cc: linux-kernel@vger.kernel.org Subject: Re: 2.6.0 schedule_tick question In-Reply-To: <200401101235.i0ACZUS12298@hofr.at> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 10 Jan 2004, Der Herr Hofrat wrote: > in 2.6.0 kernel/sched.c scheduler_tick currently the > case of rt_tasks for SCHED_RR is doing > > if ((p->policy == SCHED_RR) && !--p->time_slice) { > ... > dequeue_task(p, rq->active); > enqueue_task(p, rq->active); > > which is: > > static inline void dequeue_task(struct task_struct *p, prio_array_t *array) > { > array->nr_active--; > list_del(&p->run_list); > if (list_empty(array->queue + p->prio)) > __clear_bit(p->prio, array->bitmap); > } > > static inline void enqueue_task(struct task_struct *p, prio_array_t *array) > { > list_add_tail(&p->run_list, array->queue + p->prio); > __set_bit(p->prio, array->bitmap); > array->nr_active++; > p->array = array; > } > > looking at these two functions this looks like quite some overhead as it > actually could be reduced to: > > list_del(&p->run_list); > list_add_tail(&p->run_list, array->queue + p->prio); > > for the rest I don't see any effect it would have ? Yes, we could have a rotate_task() function but the impact is basically zero because of the little overhead compared to the frequency of the operation. - Davide