From patchwork Sat Mar 23 03:59:58 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 13600529 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A243D3FC7; Sat, 23 Mar 2024 04:07:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711166847; cv=none; b=OgwFCFCVRytWJq4iTTTv7+B7rVX6Ea4fZfCwIZB2BxyMphuDq5s07k4CdOk6Glrsh6cBILpInBDadEjSHrfoQRIhYCUfwfS064ZAWSyCvR5IqLNEZO715lW39Jvsc3O4wDOdXJZqCX9NICTKyBcvQLozfCZoKjvURGnx0w4gPrM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711166847; c=relaxed/simple; bh=XEcNbSU9WGBQkbrarjBS+xGi8ayqQQquGvvzRVhnvG8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=cJQhp2OK5q/6i78PhsD13bEJ0oXrCSoAIRPY3fMu6IXwR6XA8qzAZLrOhwoIldAMOB3OsMhrRI0It3uGryBL01/VGynzA9/BFvImMXjHv35IH7X/tu8p86jb4htbi33uidI4MdL52giboPSTdFd2HVuqxpBgdN5A1YoiYIv1Bqo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.235]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4V1lyW3qRyz4f3jsh; Sat, 23 Mar 2024 12:07:15 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 9932A1A0C11; Sat, 23 Mar 2024 12:07:21 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP1 (Coremail) with SMTP id cCh0CgAX5g51Vf5lhTs2Hw--.40826S8; Sat, 23 Mar 2024 12:07:21 +0800 (CST) From: Yu Kuai To: ming.lei@redhat.com, hch@lst.de, bvanassche@acm.org, axboe@kernel.dk, mpatocka@redhat.com, snitzer@redhat.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com Subject: [PATCH 1/2] block: support to account io_ticks precisely Date: Sat, 23 Mar 2024 11:59:58 +0800 Message-Id: <20240323035959.1397382-5-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240323035959.1397382-1-yukuai1@huaweicloud.com> References: <20240323035959.1397382-1-yukuai1@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: cCh0CgAX5g51Vf5lhTs2Hw--.40826S8 X-Coremail-Antispam: 1UD129KBjvJXoWxXw1kWF1fur4xuw43JFWxCrg_yoWrKF15pF Wq93WqyrZIgr1ruFWDJa17Ja1rG3Wvk34UZ3W3Jryayr1DKr4fAF1IvrWFvrySvrZ7AFWU uw1UAF97Aa1q937anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUQS14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkE bVWUJVW8JwCFI7km07C267AKxVWUXVWUAwC20s026c02F40E14v26r1j6r18MI8I3I0E74 80Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0 I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UMIIF0xvE42 xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF 7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjfUOyIUUUUUU X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ From: Yu Kuai Currently, io_ticks is accounted based on sampling, specifically update_io_ticks() will always account io_ticks by 1 jiffies from bdev_start_io_acct()/blk_account_io_start(), and the result can be inaccurate, for example(HZ is 250): Test script: fio -filename=/dev/sda -bs=4k -rw=write -direct=1 -name=test -thinktime=4ms Test result: util is about 90%, while the disk is really idle. This behaviour is introduced by commit 5b18b5a73760 ("block: delete part_round_stats and switch to less precise counting"), however, there was a key point that is missed that this patch also improve performance a lot: Before the commit: part_round_stats: if (part->stamp != now) stats |= 1; part_in_flight() -> there can be lots of task here in 1 jiffies. part_round_stats_single() __part_stat_add() part->stamp = now; After the commit: update_io_ticks: stamp = part->bd_stamp; if (time_after(now, stamp)) if (try_cmpxchg()) __part_stat_add() -> only one task can reach here in 1 jiffies. Hence in order to account io_ticks precisely, we only need to know if there are IO inflight at most once in one jiffies. Noted that for rq-based device, iterating tags should not be used here because 'tags->lock' is grabbed in blk_mq_find_and_get_req(), hence part_stat_lock_inc/dec() and part_in_flight() is used to trace inflight. The additional overhead is quite little: - per cpu add/dec for each IO for rq-based device; - per cpu sum for each jiffies; And it's verified by null-blk that there are no performance degration under heavy IO pressure. Fixes: 5b18b5a73760 ("block: delete part_round_stats and switch to less precise counting") Signed-off-by: Yu Kuai --- block/blk-core.c | 9 +++++---- block/blk-merge.c | 2 ++ block/blk-mq.c | 4 ++++ block/blk.h | 1 + block/genhd.c | 2 +- 5 files changed, 13 insertions(+), 5 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index a16b5abdbbf5..71c4d3982ef4 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -985,10 +985,11 @@ void update_io_ticks(struct block_device *part, unsigned long now, bool end) unsigned long stamp; again: stamp = READ_ONCE(part->bd_stamp); - if (unlikely(time_after(now, stamp))) { - if (likely(try_cmpxchg(&part->bd_stamp, &stamp, now))) - __part_stat_add(part, io_ticks, end ? now - stamp : 1); - } + if (unlikely(time_after(now, stamp)) && + likely(try_cmpxchg(&part->bd_stamp, &stamp, now)) && + (end || part_in_flight(part))) + __part_stat_add(part, io_ticks, now - stamp); + if (part->bd_partno) { part = bdev_whole(part); goto again; diff --git a/block/blk-merge.c b/block/blk-merge.c index 2a06fd33039d..c96f7f612218 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -779,6 +779,8 @@ static void blk_account_io_merge_request(struct request *req) if (blk_do_io_stat(req)) { part_stat_lock(); part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); + part_stat_local_dec(req->part, + in_flight[op_is_write(req_op(req))]); part_stat_unlock(); } } diff --git a/block/blk-mq.c b/block/blk-mq.c index 555ada922cf0..82045f0ab5ba 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1002,6 +1002,8 @@ static inline void blk_account_io_done(struct request *req, u64 now) update_io_ticks(req->part, jiffies, true); part_stat_inc(req->part, ios[sgrp]); part_stat_add(req->part, nsecs[sgrp], now - req->start_time_ns); + part_stat_local_dec(req->part, + in_flight[op_is_write(req_op(req))]); part_stat_unlock(); } } @@ -1024,6 +1026,8 @@ static inline void blk_account_io_start(struct request *req) part_stat_lock(); update_io_ticks(req->part, jiffies, false); + part_stat_local_inc(req->part, + in_flight[op_is_write(req_op(req))]); part_stat_unlock(); } } diff --git a/block/blk.h b/block/blk.h index 47960bf31543..5fc206ced744 100644 --- a/block/blk.h +++ b/block/blk.h @@ -358,6 +358,7 @@ static inline bool blk_do_io_stat(struct request *rq) } void update_io_ticks(struct block_device *part, unsigned long now, bool end); +unsigned int part_in_flight(struct block_device *part); static inline void req_set_nomerge(struct request_queue *q, struct request *req) { diff --git a/block/genhd.c b/block/genhd.c index bb29a68e1d67..782a42718965 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -118,7 +118,7 @@ static void part_stat_read_all(struct block_device *part, } } -static unsigned int part_in_flight(struct block_device *part) +unsigned int part_in_flight(struct block_device *part) { unsigned int inflight = 0; int cpu;