Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262160AbVC2CyC (ORCPT ); Mon, 28 Mar 2005 21:54:02 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262161AbVC2CyC (ORCPT ); Mon, 28 Mar 2005 21:54:02 -0500 Received: from fmr24.intel.com ([143.183.121.16]:59848 "EHLO scsfmr004.sc.intel.com") by vger.kernel.org with ESMTP id S262160AbVC2Cxz (ORCPT ); Mon, 28 Mar 2005 21:53:55 -0500 Message-Id: <200503290253.j2T2rqg25691@unix-os.sc.intel.com> From: "Chen, Kenneth W" To: Cc: Subject: [patch] use cheaper elv_queue_empty when unplug a device Date: Mon, 28 Mar 2005 18:53:49 -0800 X-Mailer: Microsoft Office Outlook, Build 11.0.6353 Thread-Index: AcU0Cogdblw5dczUTFy1c4/YC8HgbA== X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1368 Lines: 41 This patch was posted last year and if I remember correctly, Jens said he is OK with the patch. In function __generic_unplug_deivce(), kernel can use a cheaper function elv_queue_empty() instead of more expensive elv_next_request to find whether the queue is empty or not. blk_run_queue can also made conditional on whether queue's emptiness before calling request_fn(). Signed-off-by: Ken Chen --- linux-2.6.11/drivers/block/ll_rw_blk.c.orig 2005-03-28 18:22:26.000000000 -0800 +++ linux-2.6.11/drivers/block/ll_rw_blk.c 2005-03-28 18:44:46.000000000 -0800 @@ -1459,7 +1459,7 @@ void __generic_unplug_device(request_que /* * was plugged, fire request_fn if queue has stuff to do */ - if (elv_next_request(q)) + if (!elv_queue_empty(q)) q->request_fn(q); } EXPORT_SYMBOL(__generic_unplug_device); @@ -1589,7 +1589,8 @@ void blk_run_queue(struct request_queue spin_lock_irqsave(q->queue_lock, flags); blk_remove_plug(q); - q->request_fn(q); + if (!elv_queue_empty(q)) + q->request_fn(q); spin_unlock_irqrestore(q->queue_lock, flags); } EXPORT_SYMBOL(blk_run_queue); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/