From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 42B06C0015E for ; Thu, 27 Jul 2023 00:09:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229506AbjG0AJj (ORCPT ); Wed, 26 Jul 2023 20:09:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229495AbjG0AJi (ORCPT ); Wed, 26 Jul 2023 20:09:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A9EF1FDA for ; Wed, 26 Jul 2023 17:09:37 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id CACE961CE0 for ; Thu, 27 Jul 2023 00:09:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76EB4C433C8; Thu, 27 Jul 2023 00:09:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690416576; bh=OICC/lanKluUb34VQFXLxFzHy02vEomtLzfQ+XVwV98=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=G9SXUGWxZ5oqQB9kVttdfshWat5ZYgexNQ/uqcE74aqxpnx8xqwUFSru5qr8qB/S1 5pBMzXxX5r8hHXaNG4Qx6n0hndvoXp1JI17uZAJ8rG1BPITtOkbTXRn8AUAty34igV S3VQGml9xDBbBcwSlJ0gmkTr9rxv/kNbyvCpkAuC481Pl7p2fux8znDeLaJdSbSDhI Aq8PK18xUFoU4b9oyz+MwxWGGRd25RzVn30dRMtQbF5fbB2vbh7s0UFOPxTD51AFyb dMQa+Yc1uJYagQjxpuEgE6WprZ6T1BnvaU5o7NTtc7kyQOSI6SoMvUARk48CqQhMf7 nDbwlOsbABcew== Message-ID: <53514e4d-e75f-3bf0-efa2-b162b6ac73a2@kernel.org> Date: Thu, 27 Jul 2023 09:09:34 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v4 3/7] block/mq-deadline: Only use zone locking if necessary Content-Language: en-US To: Bart Van Assche , Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , "Martin K . Petersen" , Jaegeuk Kim , Ming Lei References: <20230726193440.1655149-1-bvanassche@acm.org> <20230726193440.1655149-4-bvanassche@acm.org> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <20230726193440.1655149-4-bvanassche@acm.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 7/27/23 04:34, Bart Van Assche wrote: > Measurements have shown that limiting the queue depth to one for zoned to one -> to one per zone > writes has a significant negative performance impact on zoned UFS devices. > Hence this patch that disables zone locking by the mq-deadline scheduler > if zoned writes are submitted in order and if the storage controller The "submitted in order" is actually never checked. So let's not use this in this explanation. > preserves the command order. This patch is based on the following > assumptions: > - It happens infrequently that zoned write requests are reordered by the > block layer. > - The I/O priority of all write requests is the same per zone. > - Either no I/O scheduler is used or an I/O scheduler is used that > submits write requests per zone in LBA order. > > Cc: Christoph Hellwig > Cc: Damien Le Moal > Cc: Ming Lei > Signed-off-by: Bart Van Assche > --- > block/mq-deadline.c | 25 +++++++++++++++++++------ > 1 file changed, 19 insertions(+), 6 deletions(-) > > diff --git a/block/mq-deadline.c b/block/mq-deadline.c > index 02a916ba62ee..9a64577fe942 100644 > --- a/block/mq-deadline.c > +++ b/block/mq-deadline.c > @@ -338,6 +338,17 @@ static struct request *deadline_skip_seq_writes(struct deadline_data *dd, > return rq; > } > > +/* > + * Use write locking if either QUEUE_FLAG_NO_ZONE_WRITE_LOCK or > + * REQ_NO_ZONE_WRITE_LOCK has not been set. Not using zone write locking is > + * only safe if the submitter allocates and submit requests in LBA order per > + * zone and if the block driver preserves the request order. > + */ > +static bool dd_use_write_locking(struct request *rq) Nit: maybe rename this to dd_use_zone_write_locking() to be clear this is for zoned devices only ? > +{ > + return blk_queue_is_zoned(rq->q) && !blk_no_zone_write_lock(rq); > +} > + > /* > * For the specified data direction, return the next request to > * dispatch using arrival ordered lists. > @@ -353,7 +364,7 @@ deadline_fifo_request(struct deadline_data *dd, struct dd_per_prio *per_prio, > return NULL; > > rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next); > - if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q)) > + if (data_dir == DD_READ || !dd_use_write_locking(rq)) > return rq; > > /* > @@ -398,7 +409,7 @@ deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio, > if (!rq) > return NULL; > > - if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q)) > + if (data_dir == DD_READ || !dd_use_write_locking(rq)) > return rq; > > /* > @@ -526,8 +537,9 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd, > } > > /* > - * For a zoned block device, if we only have writes queued and none of > - * them can be dispatched, rq will be NULL. > + * For a zoned block device that requires write serialization, if we > + * only have writes queued and none of them can be dispatched, rq will > + * be NULL. > */ > if (!rq) > return NULL; > @@ -552,7 +564,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd, > /* > * If the request needs its target zone locked, do it. > */ > - blk_req_zone_write_lock(rq); > + if (dd_use_write_locking(rq)) > + blk_req_zone_write_lock(rq); > rq->rq_flags |= RQF_STARTED; > return rq; > } > @@ -933,7 +946,7 @@ static void dd_finish_request(struct request *rq) > > atomic_inc(&per_prio->stats.completed); > > - if (blk_queue_is_zoned(q)) { > + if (dd_use_write_locking(rq)) { > unsigned long flags; > > spin_lock_irqsave(&dd->zone_lock, flags); -- Damien Le Moal Western Digital Research