From patchwork Wed Nov 28 00:42:12 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mikulas Patocka X-Patchwork-Id: 10701671 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4FAFF14D6 for ; Wed, 28 Nov 2018 00:43:03 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3E0502C90A for ; Wed, 28 Nov 2018 00:43:03 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 325D82C915; Wed, 28 Nov 2018 00:43:03 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,SUBJ_OBFU_PUNCT_FEW 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 791DB2C910 for ; Wed, 28 Nov 2018 00:43:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726907AbeK1Lmm (ORCPT ); Wed, 28 Nov 2018 06:42:42 -0500 Received: from 109-183-129-149.customers.tmcz.cz ([109.183.129.149]:56968 "EHLO leontynka.twibright.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726418AbeK1Lml (ORCPT ); Wed, 28 Nov 2018 06:42:41 -0500 Received: from debian.vm ([192.168.192.2]) by leontynka.twibright.com with smtp (Exim 4.89) (envelope-from ) id 1gRnwH-0007s3-Kx; Wed, 28 Nov 2018 01:42:50 +0100 Received: by debian.vm (sSMTP sendmail emulation); Wed, 28 Nov 2018 01:42:49 +0100 Message-Id: <20181128004249.147084927@debian.vm> User-Agent: quilt/0.65 Date: Wed, 28 Nov 2018 01:42:12 +0100 From: Mikulas Patocka To: Jens Axboe Cc: Mike Snitzer , dm-devel@redhat.com, linux-block@vger.kernel.org, "Alasdair G. Kergon" , Christoph Hellwig , Mikulas Patocka Subject: [PATCH 1/3] block: delete part_round_stats and switch to less precise counting MIME-Version: 1.0 Content-Disposition: inline; filename=block-delete-part_round_stats.patch 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 We want to convert to per-cpu in_flight counters. The function part_round_stats needs the in_flight counter every jiffy, it would be too costly to sum all the percpu variables every jiffy, so it must be deleted. part_round_stats is used to calculate two counters - time_in_queue and io_ticks. time_in_queue can be calculated without part_round_stats, by adding the duration of the I/O when the I/O ends (the value is almost as exact as the previously calculated value, except that time for in-progress I/Os is not counted). io_ticks can be approximated by increasing the value when I/O is started or ended and the jiffies value has changed. If the I/Os take less than a jiffy, the value is as exact as the previously calculated value. If the I/Os take more than a jiffy, io_ticks can drift behind the previously calculated value. Signed-off-by: Mikulas Patocka --- block/bio.c | 26 ++++++++++++++++-- block/blk-core.c | 64 +++------------------------------------------- block/blk-merge.c | 1 block/genhd.c | 4 -- block/partition-generic.c | 4 -- include/linux/genhd.h | 3 -- 6 files changed, 29 insertions(+), 73 deletions(-) Index: linux-block/block/bio.c =================================================================== --- linux-block.orig/block/bio.c 2018-11-26 23:44:17.000000000 +0100 +++ linux-block/block/bio.c 2018-11-26 23:44:17.000000000 +0100 @@ -1663,13 +1663,29 @@ defer: } EXPORT_SYMBOL_GPL(bio_check_pages_dirty); +void update_io_ticks(int cpu, struct hd_struct *part, unsigned long now) +{ + unsigned long stamp; +again: + stamp = READ_ONCE(part->stamp); + if (unlikely(stamp != now)) { + if (likely(cmpxchg(&part->stamp, stamp, now) == stamp)) { + __part_stat_add(cpu, part, io_ticks, 1); + } + } + if (part->partno) { + part = &part_to_disk(part)->part0; + goto again; + } +} + void generic_start_io_acct(struct request_queue *q, int op, unsigned long sectors, struct hd_struct *part) { const int sgrp = op_stat_group(op); int cpu = part_stat_lock(); - part_round_stats(q, cpu, part); + update_io_ticks(cpu, part, jiffies); part_stat_inc(cpu, part, ios[sgrp]); part_stat_add(cpu, part, sectors[sgrp], sectors); part_inc_in_flight(q, part, op_is_write(op)); @@ -1681,12 +1697,16 @@ EXPORT_SYMBOL(generic_start_io_acct); void generic_end_io_acct(struct request_queue *q, int req_op, struct hd_struct *part, unsigned long start_time) { - unsigned long duration = jiffies - start_time; + unsigned long now = jiffies; + unsigned long duration = now - start_time; const int sgrp = op_stat_group(req_op); int cpu = part_stat_lock(); + update_io_ticks(cpu, part, now); part_stat_add(cpu, part, nsecs[sgrp], jiffies_to_nsecs(duration)); - part_round_stats(q, cpu, part); + part_stat_add(cpu, part, time_in_queue, duration); + if (part->partno) + part_stat_add(cpu, &part_to_disk(part)->part0, time_in_queue, duration); part_dec_in_flight(q, part, op_is_write(req_op)); part_stat_unlock(); Index: linux-block/block/blk-core.c =================================================================== --- linux-block.orig/block/blk-core.c 2018-11-26 23:44:17.000000000 +0100 +++ linux-block/block/blk-core.c 2018-11-26 23:44:17.000000000 +0100 @@ -583,63 +583,6 @@ struct request *blk_get_request(struct r } EXPORT_SYMBOL(blk_get_request); -static void part_round_stats_single(struct request_queue *q, int cpu, - struct hd_struct *part, unsigned long now, - unsigned int inflight) -{ - if (inflight) { - __part_stat_add(cpu, part, time_in_queue, - inflight * (now - part->stamp)); - __part_stat_add(cpu, part, io_ticks, (now - part->stamp)); - } - part->stamp = now; -} - -/** - * part_round_stats() - Round off the performance stats on a struct disk_stats. - * @q: target block queue - * @cpu: cpu number for stats access - * @part: target partition - * - * The average IO queue length and utilisation statistics are maintained - * by observing the current state of the queue length and the amount of - * time it has been in this state for. - * - * Normally, that accounting is done on IO completion, but that can result - * in more than a second's worth of IO being accounted for within any one - * second, leading to >100% utilisation. To deal with that, we call this - * function to do a round-off before returning the results when reading - * /proc/diskstats. This accounts immediately for all queue usage up to - * the current jiffies and restarts the counters again. - */ -void part_round_stats(struct request_queue *q, int cpu, struct hd_struct *part) -{ - struct hd_struct *part2 = NULL; - unsigned long now = jiffies; - unsigned int inflight[2]; - int stats = 0; - - if (part->stamp != now) - stats |= 1; - - if (part->partno) { - part2 = &part_to_disk(part)->part0; - if (part2->stamp != now) - stats |= 2; - } - - if (!stats) - return; - - part_in_flight(q, part, inflight); - - if (stats & 2) - part_round_stats_single(q, cpu, part2, now, inflight[1]); - if (stats & 1) - part_round_stats_single(q, cpu, part, now, inflight[0]); -} -EXPORT_SYMBOL_GPL(part_round_stats); - void blk_put_request(struct request *req) { blk_mq_free_request(req); @@ -1408,9 +1351,11 @@ void blk_account_io_done(struct request cpu = part_stat_lock(); part = req->part; + update_io_ticks(cpu, part, jiffies); part_stat_inc(cpu, part, ios[sgrp]); part_stat_add(cpu, part, nsecs[sgrp], now - req->start_time_ns); - part_round_stats(req->q, cpu, part); + part_stat_add(cpu, part, time_in_queue, nsecs_to_jiffies64(now - req->start_time_ns)); + part_stat_add(cpu, &part_to_disk(part)->part0, time_in_queue, nsecs_to_jiffies64(now - req->start_time_ns)); part_dec_in_flight(req->q, part, rq_data_dir(req)); hd_struct_put(part); @@ -1446,11 +1391,12 @@ void blk_account_io_start(struct request part = &rq->rq_disk->part0; hd_struct_get(part); } - part_round_stats(rq->q, cpu, part); part_inc_in_flight(rq->q, part, rw); rq->part = part; } + update_io_ticks(cpu, part, jiffies); + part_stat_unlock(); } Index: linux-block/block/blk-merge.c =================================================================== --- linux-block.orig/block/blk-merge.c 2018-11-26 23:44:17.000000000 +0100 +++ linux-block/block/blk-merge.c 2018-11-26 23:44:17.000000000 +0100 @@ -690,7 +690,6 @@ static void blk_account_io_merge(struct cpu = part_stat_lock(); part = req->part; - part_round_stats(req->q, cpu, part); part_dec_in_flight(req->q, part, rq_data_dir(req)); hd_struct_put(part); Index: linux-block/block/genhd.c =================================================================== --- linux-block.orig/block/genhd.c 2018-11-26 23:44:17.000000000 +0100 +++ linux-block/block/genhd.c 2018-11-26 23:44:17.000000000 +0100 @@ -1326,7 +1326,6 @@ static int diskstats_show(struct seq_fil struct hd_struct *hd; char buf[BDEVNAME_SIZE]; unsigned int inflight[2]; - int cpu; /* if (&disk_to_dev(gp)->kobj.entry == block_class.devices.next) @@ -1338,9 +1337,6 @@ static int diskstats_show(struct seq_fil disk_part_iter_init(&piter, gp, DISK_PITER_INCL_EMPTY_PART0); while ((hd = disk_part_iter_next(&piter))) { - cpu = part_stat_lock(); - part_round_stats(gp->queue, cpu, hd); - part_stat_unlock(); part_in_flight(gp->queue, hd, inflight); seq_printf(seqf, "%4d %7d %s " "%lu %lu %lu %u " Index: linux-block/block/partition-generic.c =================================================================== --- linux-block.orig/block/partition-generic.c 2018-11-26 23:44:17.000000000 +0100 +++ linux-block/block/partition-generic.c 2018-11-26 23:44:17.000000000 +0100 @@ -121,11 +121,7 @@ ssize_t part_stat_show(struct device *de struct hd_struct *p = dev_to_part(dev); struct request_queue *q = part_to_disk(p)->queue; unsigned int inflight[2]; - int cpu; - cpu = part_stat_lock(); - part_round_stats(q, cpu, p); - part_stat_unlock(); part_in_flight(q, p, inflight); return sprintf(buf, "%8lu %8lu %8llu %8u " Index: linux-block/include/linux/genhd.h =================================================================== --- linux-block.orig/include/linux/genhd.h 2018-11-26 23:44:17.000000000 +0100 +++ linux-block/include/linux/genhd.h 2018-11-26 23:44:17.000000000 +0100 @@ -398,8 +398,7 @@ static inline void free_part_info(struct kfree(part->info); } -/* block/blk-core.c */ -extern void part_round_stats(struct request_queue *q, int cpu, struct hd_struct *part); +void update_io_ticks(int cpu, struct hd_struct *part, unsigned long now); /* block/genhd.c */ extern void device_add_disk(struct device *parent, struct gendisk *disk,