From patchwork Fri Aug 6 02:08:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 12422535 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BB9E4C4320A for ; Fri, 6 Aug 2021 01:57:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9721860E09 for ; Fri, 6 Aug 2021 01:57:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241743AbhHFB55 (ORCPT ); Thu, 5 Aug 2021 21:57:57 -0400 Received: from szxga08-in.huawei.com ([45.249.212.255]:13239 "EHLO szxga08-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230282AbhHFB54 (ORCPT ); Thu, 5 Aug 2021 21:57:56 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4GgpWv1HMtz1CSrh; Fri, 6 Aug 2021 09:57:31 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Fri, 6 Aug 2021 09:57:39 +0800 Received: from huawei.com (10.175.127.227) by dggema762-chm.china.huawei.com (10.1.198.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Fri, 6 Aug 2021 09:57:38 +0800 From: Yu Kuai To: , CC: , , , Subject: [PATCH v2 1/4] block, bfq: add support to track if root_group have any pending requests Date: Fri, 6 Aug 2021 10:08:23 +0800 Message-ID: <20210806020826.1407257-2-yukuai3@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210806020826.1407257-1-yukuai3@huawei.com> References: <20210806020826.1407257-1-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema762-chm.china.huawei.com (10.1.198.204) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Add a new member in bfq_data to track number of queues that are in root_group with any pending requests. This will be used in next patch to optmize queue idle judgment when root_group doesn't have any pending requests. Signed-off-by: Yu Kuai --- block/bfq-iosched.c | 8 +++++++- block/bfq-iosched.h | 13 +++++++++++-- block/bfq-wf2q.c | 37 ++++++++++++++++++++++++------------- 3 files changed, 42 insertions(+), 16 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 727955918563..7c6b412f9a9c 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -859,8 +859,14 @@ void __bfq_weights_tree_remove(struct bfq_data *bfqd, void bfq_weights_tree_remove(struct bfq_data *bfqd, struct bfq_queue *bfqq) { - struct bfq_entity *entity = bfqq->entity.parent; + struct bfq_entity *entity = &bfqq->entity; + + if (entity->in_groups_with_pending_reqs) { + entity->in_groups_with_pending_reqs = false; + bfqd->num_queues_with_pending_reqs_in_root--; + } + entity = entity->parent; for_each_entity(entity) { struct bfq_sched_data *sd = entity->my_sched_data; diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 99c2a3cb081e..610769214f72 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -195,7 +195,12 @@ struct bfq_entity { /* flag, set to request a weight, ioprio or ioprio_class change */ int prio_changed; - /* flag, set if the entity is counted in groups_with_pending_reqs */ + /* + * If entity represents bfq_group, this flag will set if the group is + * not root_group and have any pending requests; If entity represents + * bfq_queue, this flag will set if the queue is in root_group and have + * any pending requests. + */ bool in_groups_with_pending_reqs; /* last child queue of entity created (for non-leaf entities) */ @@ -539,7 +544,11 @@ struct bfq_data { * with no request waiting for completion. */ unsigned int num_groups_with_pending_reqs; - + /* + * number of queues that are in root_group with at least one request + * waiting for completion. + */ + unsigned int num_queues_with_pending_reqs_in_root; /* * Per-class (RT, BE, IDLE) number of bfq_queues containing * requests (including the queue in service, even if it is diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c index 7a462df71f68..188c8f907219 100644 --- a/block/bfq-wf2q.c +++ b/block/bfq-wf2q.c @@ -946,6 +946,29 @@ static void bfq_update_fin_time_enqueue(struct bfq_entity *entity, bfq_active_insert(st, entity); } +static void bfq_update_groups_with_pending_reqs(struct bfq_entity *entity) +{ +#ifdef CONFIG_BFQ_GROUP_IOSCHED + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + + if (bfqq) { + if (!entity->parent && !entity->in_groups_with_pending_reqs) { + entity->in_groups_with_pending_reqs = true; + bfqq->bfqd->num_queues_with_pending_reqs_in_root++; + } + } else { + if (!entity->in_groups_with_pending_reqs) { + struct bfq_group *bfqg = + container_of(entity, struct bfq_group, entity); + struct bfq_data *bfqd = bfqg->bfqd; + + entity->in_groups_with_pending_reqs = true; + bfqd->num_groups_with_pending_reqs++; + } + } +#endif +} + /** * __bfq_activate_entity - handle activation of entity. * @entity: the entity being activated. @@ -999,19 +1022,7 @@ static void __bfq_activate_entity(struct bfq_entity *entity, entity->on_st_or_in_serv = true; } -#ifdef CONFIG_BFQ_GROUP_IOSCHED - if (!bfq_entity_to_bfqq(entity)) { /* bfq_group */ - struct bfq_group *bfqg = - container_of(entity, struct bfq_group, entity); - struct bfq_data *bfqd = bfqg->bfqd; - - if (!entity->in_groups_with_pending_reqs) { - entity->in_groups_with_pending_reqs = true; - bfqd->num_groups_with_pending_reqs++; - } - } -#endif - + bfq_update_groups_with_pending_reqs(entity); bfq_update_fin_time_enqueue(entity, st, backshifted); } From patchwork Fri Aug 6 02:08:24 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 12422539 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF2BCC4320E for ; Fri, 6 Aug 2021 01:57:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B501460C51 for ; Fri, 6 Aug 2021 01:57:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231893AbhHFB56 (ORCPT ); Thu, 5 Aug 2021 21:57:58 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:7795 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231993AbhHFB54 (ORCPT ); Thu, 5 Aug 2021 21:57:56 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4GgpWv6c3LzYlXr; Fri, 6 Aug 2021 09:57:31 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Fri, 6 Aug 2021 09:57:39 +0800 Received: from huawei.com (10.175.127.227) by dggema762-chm.china.huawei.com (10.1.198.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Fri, 6 Aug 2021 09:57:38 +0800 From: Yu Kuai To: , CC: , , , Subject: [PATCH v2 2/4] block, bfq: do not idle if only one cgroup is activated Date: Fri, 6 Aug 2021 10:08:24 +0800 Message-ID: <20210806020826.1407257-3-yukuai3@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210806020826.1407257-1-yukuai3@huawei.com> References: <20210806020826.1407257-1-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema762-chm.china.huawei.com (10.1.198.204) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org If only one group is activated, there is no need to guarantee the same share of the throughput of queues in the same group. If CONFIG_BFQ_GROUP_IOSCHED is enabled, there is no need to check 'varied_queue_weights' and 'multiple_classes_busy': 1) num_groups_with_pending_reqs = 0, idle is not needed 2) num_groups_with_pending_reqs = 1 - if root group have any pending requests, idle is needed - if root group is idle, idle is not needed 3) num_groups_with_pending_reqs > 1, idle is needed Test procedure: run "fio -numjobs=1 -ioengine=psync -bs=4k -direct=1 -rw=randread..." multiple times in the same cgroup(not root). Test result: total bandwidth(Mib/s) | total jobs | before this patch | after this patch | | ---------- | ----------------- | --------------------- | | 1 | 33.8 | 33.8 | | 2 | 33.8 | 65.4 (32.7 each job) | | 4 | 33.8 | 106.8 (26.7 each job) | | 8 | 33.8 | 126.4 (15.8 each job) | By the way, if I test with "fio -numjobs=1/2/4/8 ...", test result is the same with or without this patch. Signed-off-by: Yu Kuai --- block/bfq-iosched.c | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 7c6b412f9a9c..a780205a1be4 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -709,7 +709,9 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq) * much easier to maintain the needed state: * 1) all active queues have the same weight, * 2) all active queues belong to the same I/O-priority class, - * 3) there are no active groups. + * 3) there are one active group at most(incluing root_group). + * If the last condition is false, there is no need to guarantee the, + * same share of the throughput of queues in the same group. * In particular, the last condition is always true if hierarchical * support or the cgroups interface are not enabled, thus no state * needs to be maintained in this case. @@ -717,7 +719,26 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq) static bool bfq_asymmetric_scenario(struct bfq_data *bfqd, struct bfq_queue *bfqq) { - bool smallest_weight = bfqq && + bool smallest_weight; + bool varied_queue_weights; + bool multiple_classes_busy; + +#ifdef CONFIG_BFQ_GROUP_IOSCHED + if (bfqd->num_groups_with_pending_reqs > 1) + return true; + + if (bfqd->num_groups_with_pending_reqs && + bfqd->num_queues_with_pending_reqs_in_root) + return true; + + /* + * Reach here means only one group(incluing root group) has pending + * requests, thus it's safe to return. + */ + return false; +#endif + + smallest_weight = bfqq && bfqq->weight_counter && bfqq->weight_counter == container_of( @@ -729,21 +750,17 @@ static bool bfq_asymmetric_scenario(struct bfq_data *bfqd, * For queue weights to differ, queue_weights_tree must contain * at least two nodes. */ - bool varied_queue_weights = !smallest_weight && + varied_queue_weights = !smallest_weight && !RB_EMPTY_ROOT(&bfqd->queue_weights_tree.rb_root) && (bfqd->queue_weights_tree.rb_root.rb_node->rb_left || bfqd->queue_weights_tree.rb_root.rb_node->rb_right); - bool multiple_classes_busy = + multiple_classes_busy = (bfqd->busy_queues[0] && bfqd->busy_queues[1]) || (bfqd->busy_queues[0] && bfqd->busy_queues[2]) || (bfqd->busy_queues[1] && bfqd->busy_queues[2]); - return varied_queue_weights || multiple_classes_busy -#ifdef CONFIG_BFQ_GROUP_IOSCHED - || bfqd->num_groups_with_pending_reqs > 0 -#endif - ; + return varied_queue_weights || multiple_classes_busy; } /* From patchwork Fri Aug 6 02:08:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 12422533 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DF73C4338F for ; Fri, 6 Aug 2021 01:57:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7FDEB60C51 for ; Fri, 6 Aug 2021 01:57:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230012AbhHFB55 (ORCPT ); Thu, 5 Aug 2021 21:57:57 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:13286 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231893AbhHFB54 (ORCPT ); Thu, 5 Aug 2021 21:57:56 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4GgpQR1050z83BF; Fri, 6 Aug 2021 09:52:47 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Fri, 6 Aug 2021 09:57:39 +0800 Received: from huawei.com (10.175.127.227) by dggema762-chm.china.huawei.com (10.1.198.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Fri, 6 Aug 2021 09:57:39 +0800 From: Yu Kuai To: , CC: , , , Subject: [PATCH v2 3/4] block, bfq: add support to record request size information Date: Fri, 6 Aug 2021 10:08:25 +0800 Message-ID: <20210806020826.1407257-4-yukuai3@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210806020826.1407257-1-yukuai3@huawei.com> References: <20210806020826.1407257-1-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema762-chm.china.huawei.com (10.1.198.204) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org If bfq keep dispatching requests with same size, the following information are stored if CONFIG_BFQ_GROUP_IOSCHED is enabled: 1) the size 2) the count of requests 3) when the first request was dispatched These will be used in later patch to support concurrent sync io in such situation. Signed-off-by: Yu Kuai --- block/bfq-iosched.c | 15 +++++++++++++++ block/bfq-iosched.h | 16 ++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index a780205a1be4..7df3fc0ef4ef 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -4936,6 +4936,20 @@ static bool bfq_has_work(struct blk_mq_hw_ctx *hctx) bfq_tot_busy_queues(bfqd) > 0; } +static void bfq_update_dispatch_size_info(struct bfq_data *bfqd, + unsigned int size) +{ +#ifdef CONFIG_BFQ_GROUP_IOSCHED + if (bfqd->dispatch_size == size) { + bfqd->dispatch_count++; + } else { + bfqd->dispatch_size = size; + bfqd->dispatch_count = 1; + bfqd->dispatch_time = jiffies; + } +#endif +} + static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) { struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; @@ -5019,6 +5033,7 @@ static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) bfqd->rq_in_driver++; start_rq: rq->rq_flags |= RQF_STARTED; + bfq_update_dispatch_size_info(bfqd, blk_rq_bytes(rq)); } exit: return rq; diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 610769214f72..9ab498839e7c 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -777,6 +777,22 @@ struct bfq_data { * function) */ unsigned int word_depths[2][2]; + +#ifdef CONFIG_BFQ_GROUP_IOSCHED + /* the size of last dispatched request */ + unsigned int dispatch_size; + /* + * If bfq keep dispatching requests with same size, this store the + * count of requests. We use unsigned long here, so we don't care + * about overflow. + */ + unsigned long dispatch_count; + /* + * If bfq keep dispatching requests with same size, this store the + * time when the first request was dispatched. + */ + unsigned long dispatch_time; +#endif }; enum bfqq_state_flags { From patchwork Fri Aug 6 02:08:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 12422537 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3863CC432BE for ; Fri, 6 Aug 2021 01:57:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 12FE061184 for ; Fri, 6 Aug 2021 01:57:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242178AbhHFB56 (ORCPT ); Thu, 5 Aug 2021 21:57:58 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:12459 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232728AbhHFB54 (ORCPT ); Thu, 5 Aug 2021 21:57:56 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4GgpRx1bfBzckl9; Fri, 6 Aug 2021 09:54:05 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Fri, 6 Aug 2021 09:57:40 +0800 Received: from huawei.com (10.175.127.227) by dggema762-chm.china.huawei.com (10.1.198.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Fri, 6 Aug 2021 09:57:39 +0800 From: Yu Kuai To: , CC: , , , Subject: [PATCH v2 4/4] block, bfq: consider request size in bfq_asymmetric_scenario() Date: Fri, 6 Aug 2021 10:08:26 +0800 Message-ID: <20210806020826.1407257-5-yukuai3@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210806020826.1407257-1-yukuai3@huawei.com> References: <20210806020826.1407257-1-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema762-chm.china.huawei.com (10.1.198.204) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org There is a special case when bfq do not need to idle when more than one groups is active: 1) all active queues have the same weight, 2) all active queues have the same request size. 3) all active queues belong to the same I/O-priority class, Each time a request is dispatched, bfq can switch in service queue safely, since the throughput of each active queue is guaranteed to be equivalent. Test procedure: run "fio -numjobs=1 -ioengine=psync -bs=4k -direct=1 -rw=randread..." in different cgroup(not root). Test result: total bandwidth(Mib/s) | total jobs | before this patch | after this patch | | ---------- | ----------------- | --------------------- | | 1 | 33.8 | 33.8 | | 2 | 33.8 | 65.4 (32.7 each job) | | 4 | 33.8 | 106.8 (26.7 each job) | | 8 | 33.8 | 126.4 (15.8 each job) | Signed-off-by: Yu Kuai --- block/bfq-iosched.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 7df3fc0ef4ef..e5a07bd1fd84 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -268,6 +268,16 @@ static struct kmem_cache *bfq_pool; */ #define BFQ_RATE_SHIFT 16 +/* + * 1) bfq keep dispatching requests with same size for at least one second. + * 2) bfq dispatch at lease 1024 requests + * + * We think bfq are dispatching request with same size if the above two + * conditions hold true. + */ +#define VARIED_REQUEST_SIZE(bfqd) ((bfqd)->dispatch_count < 1024 ||\ + time_before(jiffies, (bfqd)->dispatch_time + HZ)) + /* * When configured for computing the duration of the weight-raising * for interactive queues automatically (see the comments at the @@ -724,7 +734,8 @@ static bool bfq_asymmetric_scenario(struct bfq_data *bfqd, bool multiple_classes_busy; #ifdef CONFIG_BFQ_GROUP_IOSCHED - if (bfqd->num_groups_with_pending_reqs > 1) + if (bfqd->num_groups_with_pending_reqs > 1 && + VARIED_REQUEST_SIZE(bfqd)) return true; if (bfqd->num_groups_with_pending_reqs &&