From patchwork Sat Nov 12 05:11:27 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jens Axboe X-Patchwork-Id: 9423915 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 F164760720 for ; Sat, 12 Nov 2016 05:12:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E1A9329AD3 for ; Sat, 12 Nov 2016 05:12:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D346629ACF; Sat, 12 Nov 2016 05:12:09 +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=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID 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 1BC16299F8 for ; Sat, 12 Nov 2016 05:12:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751257AbcKLFMG (ORCPT ); Sat, 12 Nov 2016 00:12:06 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:59649 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750775AbcKLFMF (ORCPT ); Sat, 12 Nov 2016 00:12:05 -0500 Received: from pps.filterd (m0089730.ppops.net [127.0.0.1]) by m0089730.ppops.net (8.16.0.17/8.16.0.17) with SMTP id uAC53ccm013739; Fri, 11 Nov 2016 21:11:35 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-type; s=facebook; bh=afB17L+ssg+cIOYZwmZRGJ5u3T+aDarl0acizVAR298=; b=Ycnly79cfZrJAjvwqP8CzLZ+nxd6vSVeW6XW8dHISsYAB7aU58gT6MCxA+gpE34YQ8dQ gGLfF2qzSDfxuflM/9/effr6I2yo7MB0MejKxQndQO3dDLQ7ioQye/BQ087iq5rFDAlF k29gv/lc+hnmUM4lsVH8f2uqku3bzwF3CLM= Received: from mail.thefacebook.com ([199.201.64.23]) by m0089730.ppops.net with ESMTP id 26nkt8uuum-3 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NOT); Fri, 11 Nov 2016 21:11:35 -0800 Received: from localhost.localdomain (192.168.54.13) by mail.TheFacebook.com (192.168.16.18) with Microsoft SMTP Server (TLS) id 14.3.294.0; Fri, 11 Nov 2016 21:11:34 -0800 From: Jens Axboe To: , , CC: , Jens Axboe Subject: [PATCH 3/3] blk-mq: make the polling code adaptive Date: Fri, 11 Nov 2016 22:11:27 -0700 Message-ID: <1478927487-12998-4-git-send-email-axboe@fb.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1478927487-12998-1-git-send-email-axboe@fb.com> References: <1478927487-12998-1-git-send-email-axboe@fb.com> MIME-Version: 1.0 X-Originating-IP: [192.168.54.13] X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2016-11-12_01:, , signatures=0 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 The previous commit introduced the hybrid sleep/poll mode. Take that one step further, and use the completion latencies to automatically sleep for half the mean completion time. This is a good approximation. This changes the 'io_poll_delay' sysfs file a bit to expose the various options. Depending on the value, the polling code will behave differently: -1 Never enter hybrid sleep mode 0 Use half of the completion mean for the sleep delay >0 Use this specific value as the sleep delay Signed-off-by: Jens Axboe --- block/blk-mq.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++---- block/blk-sysfs.c | 26 ++++++++++++------ include/linux/blkdev.h | 2 +- 3 files changed, 88 insertions(+), 14 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 2c77a2da123a..70b1b59ed0d3 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2125,6 +2125,11 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, */ q->nr_requests = set->queue_depth; + /* + * Default to classic polling + */ + q->poll_nsec = -1; + if (set->ops->complete) blk_queue_softirq_done(q, set->ops->complete); @@ -2462,13 +2467,70 @@ void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues) } EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues); +static unsigned long blk_mq_poll_nsecs(struct request_queue *q, + struct blk_mq_hw_ctx *hctx, + struct request *rq) +{ + struct blk_rq_stat stat[2]; + unsigned long ret = 0; + + /* + * If stats collection isn't on, don't sleep but turn it on for + * future users + */ + if (!blk_stat_enable(q)) + return 0; + + /* + * We don't have to do this once per IO, should optimize this + * to just use the current window of stats until it changes + */ + memset(&stat, 0, sizeof(stat)); + blk_hctx_stat_get(hctx, stat); + + /* + * As an optimistic guess, use half of the mean service time + * for this type of request. We can (and should) make this smarter. + * For instance, if the completion latencies are tight, we can + * get closer than just half the mean. This is especially + * important on devices where the completion latencies are longer + * than ~10 usec. + */ + if (req_op(rq) == REQ_OP_READ && stat[BLK_STAT_READ].nr_samples) + ret = (stat[BLK_STAT_READ].mean + 1) / 2; + else if (req_op(rq) == REQ_OP_WRITE && stat[BLK_STAT_WRITE].nr_samples) + ret = (stat[BLK_STAT_WRITE].mean + 1) / 2; + + return ret; +} + static bool blk_mq_poll_hybrid_sleep(struct request_queue *q, + struct blk_mq_hw_ctx *hctx, struct request *rq) { struct hrtimer_sleeper hs; + enum hrtimer_mode mode; + unsigned int nsecs; ktime_t kt; - if (!q->poll_nsec || test_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags)) + if (test_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags)) + return false; + + /* + * poll_nsec can be: + * + * -1: don't ever hybrid sleep + * 0: use half of prev avg + * >0: use this specific value + */ + if (q->poll_nsec == -1) + return false; + else if (q->poll_nsec > 0) + nsecs = q->poll_nsec; + else + nsecs = blk_mq_poll_nsecs(q, hctx, rq); + + if (!nsecs) return false; set_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags); @@ -2477,9 +2539,10 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q, * This will be replaced with the stats tracking code, using * 'avg_completion_time / 2' as the pre-sleep target. */ - kt = ktime_set(0, q->poll_nsec); + kt = ktime_set(0, nsecs); - hrtimer_init_on_stack(&hs.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + mode = HRTIMER_MODE_REL; + hrtimer_init_on_stack(&hs.timer, CLOCK_MONOTONIC, mode); hrtimer_set_expires(&hs.timer, kt); hrtimer_init_sleeper(&hs, current); @@ -2487,10 +2550,11 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q, if (test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags)) break; set_current_state(TASK_UNINTERRUPTIBLE); - hrtimer_start_expires(&hs.timer, HRTIMER_MODE_REL); + hrtimer_start_expires(&hs.timer, mode); if (hs.task) io_schedule(); hrtimer_cancel(&hs.timer); + mode = HRTIMER_MODE_ABS; } while (hs.task && !signal_pending(current)); __set_current_state(TASK_RUNNING); @@ -2510,7 +2574,7 @@ static bool __blk_mq_poll(struct blk_mq_hw_ctx *hctx, struct request *rq) * the IO isn't complete, we'll get called again and will go * straight to the busy poll loop. */ - if (blk_mq_poll_hybrid_sleep(q, rq)) + if (blk_mq_poll_hybrid_sleep(q, hctx, rq)) return true; hctx->poll_considered++; diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index b87f992fdbd7..652a36eef00c 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -352,24 +352,34 @@ queue_rq_affinity_store(struct request_queue *q, const char *page, size_t count) static ssize_t queue_poll_delay_show(struct request_queue *q, char *page) { - return queue_var_show(q->poll_nsec / 1000, page); + int val; + + if (q->poll_nsec == -1) + val = -1; + else + val = q->poll_nsec / 1000; + + return sprintf(page, "%d\n", val); } static ssize_t queue_poll_delay_store(struct request_queue *q, const char *page, size_t count) { - unsigned long poll_usec; - ssize_t ret; + int err, val; if (!q->mq_ops || !q->mq_ops->poll) return -EINVAL; - ret = queue_var_store(&poll_usec, page, count); - if (ret < 0) - return ret; + err = kstrtoint(page, 10, &val); + if (err < 0) + return err; - q->poll_nsec = poll_usec * 1000; - return ret; + if (val == -1) + q->poll_nsec = -1; + else + q->poll_nsec = val * 1000; + + return count; } static ssize_t queue_poll_show(struct request_queue *q, char *page) diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 37ed4ea705c8..85699bc90a51 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -509,7 +509,7 @@ struct request_queue { unsigned int request_fn_active; unsigned int rq_timeout; - unsigned int poll_nsec; + int poll_nsec; struct timer_list timeout; struct work_struct timeout_work; struct list_head timeout_list;