From patchwork Sun Sep 24 07:02:47 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Damien Le Moal X-Patchwork-Id: 9967795 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 408E56020C for ; Sun, 24 Sep 2017 07:03:15 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 341EC21C9A for ; Sun, 24 Sep 2017 07:03:15 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2906C28478; Sun, 24 Sep 2017 07:03:15 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8EEA221C9A for ; Sun, 24 Sep 2017 07:03:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751925AbdIXHDN (ORCPT ); Sun, 24 Sep 2017 03:03:13 -0400 Received: from esa1.hgst.iphmx.com ([68.232.141.245]:35286 "EHLO esa1.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751847AbdIXHDK (ORCPT ); Sun, 24 Sep 2017 03:03:10 -0400 X-IronPort-AV: E=Sophos;i="5.42,431,1500912000"; d="scan'208";a="156248381" Received: from sjappemgw12.hgst.com (HELO sjappemgw11.hgst.com) ([199.255.44.66]) by ob1.hgst.iphmx.com with ESMTP; 24 Sep 2017 15:03:10 +0800 Received: from washi.fujisawa.hgst.com ([10.149.53.254]) by sjappemgw11.hgst.com with ESMTP; 24 Sep 2017 00:03:09 -0700 From: Damien Le Moal To: linux-scsi@vger.kernel.org, "Martin K . Petersen" , linux-block@vger.kernel.org, Jens Axboe Cc: Christoph Hellwig , Bart Van Assche Subject: [PATCH V4 16/16] block: mq-deadline: Update documentation Date: Sun, 24 Sep 2017 16:02:47 +0900 Message-Id: <20170924070247.25560-17-damien.lemoal@wdc.com> X-Mailer: git-send-email 2.13.5 In-Reply-To: <20170924070247.25560-1-damien.lemoal@wdc.com> References: <20170924070247.25560-1-damien.lemoal@wdc.com> Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Added description of the zones_wlock tunable attribute. Signed-off-by: Damien Le Moal --- Documentation/block/deadline-iosched.txt | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/Documentation/block/deadline-iosched.txt b/Documentation/block/deadline-iosched.txt index 2d82c80322cb..b532304d2bf4 100644 --- a/Documentation/block/deadline-iosched.txt +++ b/Documentation/block/deadline-iosched.txt @@ -69,6 +69,23 @@ Front merges may still occur due to the cached last_merge hint, but since that comes at basically 0 cost we leave that on. We simply disable the rbtree front sector lookup when the io scheduler merge function is called. +zones_wlock (bool) +----------- + +(mq-deadlines only) +The blk-mq version of the deadline I/O scheduler, mq-deadline, introduced +support for zoned block devices. This added support prevents dispatching of more +than one write command per zone of the device to avoid write sequence reordering +due to the possible concurrent execution of many blk-mq operations, in +particular request dispatching. This is achieved using a per zone lock +implemented as a bitmap. When a write request is dispatched, the target zone of +the request is locked, preventing further dispatch of write requests to it +(there are no limitations on read commands). The zones_wlock tunable allows +disabling zone write locking for host aware zoned block devices as these drive +can handle random writes to zones in firmware. This tunable default setting +cannot be changed for host managed disks (always enabled) and regular disks +(always disabled). + Nov 11 2002, Jens Axboe