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 X-Spam-Level: X-Spam-Status: No, score=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 4F82BC433E2 for ; Thu, 17 Sep 2020 10:36:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 06FAC2072E for ; Thu, 17 Sep 2020 10:36:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726605AbgIQKgM (ORCPT ); Thu, 17 Sep 2020 06:36:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:34176 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726185AbgIQKfw (ORCPT ); Thu, 17 Sep 2020 06:35:52 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0F193AF74; Thu, 17 Sep 2020 10:36:15 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id E12DF1E12E1; Thu, 17 Sep 2020 12:35:40 +0200 (CEST) Date: Thu, 17 Sep 2020 12:35:40 +0200 From: Jan Kara To: Christoph Hellwig Cc: Jens Axboe , Song Liu , Hans de Goede , Richard Weinberger , Minchan Kim , linux-mtd@lists.infradead.org, dm-devel@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, drbd-dev@lists.linbit.com, linux-raid@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org Subject: Re: [PATCH 06/12] block: lift setting the readahead size into the block layer Message-ID: <20200917103540.GL7347@quack2.suse.cz> References: <20200910144833.742260-1-hch@lst.de> <20200910144833.742260-7-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200910144833.742260-7-hch@lst.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On Thu 10-09-20 16:48:26, Christoph Hellwig wrote: > Drivers shouldn't really mess with the readahead size, as that is a VM > concept. Instead set it based on the optimal I/O size by lifting the > algorithm from the md driver when registering the disk. Also set > bdi->io_pages there as well by applying the same scheme based on > max_sectors. > > Signed-off-by: Christoph Hellwig > --- > block/blk-settings.c | 5 ++--- > block/blk-sysfs.c | 10 +++++++++- > block/genhd.c | 5 +++-- > drivers/block/aoe/aoeblk.c | 2 -- > drivers/block/drbd/drbd_nl.c | 12 +----------- > drivers/md/bcache/super.c | 4 ---- > drivers/md/dm-table.c | 3 --- > drivers/md/raid0.c | 16 ---------------- > drivers/md/raid10.c | 24 +----------------------- > drivers/md/raid5.c | 13 +------------ > 10 files changed, 17 insertions(+), 77 deletions(-) > > diff --git a/block/blk-settings.c b/block/blk-settings.c > index 76a7e03bcd6cac..01049e9b998f1d 100644 > --- a/block/blk-settings.c > +++ b/block/blk-settings.c > @@ -452,6 +452,8 @@ EXPORT_SYMBOL(blk_limits_io_opt); > void blk_queue_io_opt(struct request_queue *q, unsigned int opt) > { > blk_limits_io_opt(&q->limits, opt); > + q->backing_dev_info->ra_pages = > + max(queue_io_opt(q) * 2 / PAGE_SIZE, VM_READAHEAD_PAGES); > } > EXPORT_SYMBOL(blk_queue_io_opt); > > @@ -628,9 +630,6 @@ void disk_stack_limits(struct gendisk *disk, struct block_device *bdev, > printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n", > top, bottom); > } > - > - t->backing_dev_info->io_pages = > - t->limits.max_sectors >> (PAGE_SHIFT - 9); > } > EXPORT_SYMBOL(disk_stack_limits); > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index 81722cdcf0cb21..95eb35324e1a61 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -245,7 +245,6 @@ queue_max_sectors_store(struct request_queue *q, const char *page, size_t count) > > spin_lock_irq(&q->queue_lock); > q->limits.max_sectors = max_sectors_kb << 1; > - q->backing_dev_info->io_pages = max_sectors_kb >> (PAGE_SHIFT - 10); > spin_unlock_irq(&q->queue_lock); So do I get it right that readahead won't now be limited if you store lower value to max_sectors? Why? I'd consider io_pages a "cached value" of max_sectors and thus expect it to change together with max_sectors... > @@ -854,6 +853,15 @@ int blk_register_queue(struct gendisk *disk) > percpu_ref_switch_to_percpu(&q->q_usage_counter); > } > > + /* > + * For read-ahead of large files to be effective, we need to read ahead > + * at least twice the optimal I/O size. > + */ > + q->backing_dev_info->ra_pages = > + max(queue_io_opt(q) * 2 / PAGE_SIZE, VM_READAHEAD_PAGES); > + q->backing_dev_info->io_pages = > + queue_max_sectors(q) >> (PAGE_SHIFT - 9); > + > ret = blk_trace_init_sysfs(dev); > if (ret) > return ret; > diff --git a/block/genhd.c b/block/genhd.c > index 081f1039d9367f..db311a14ddc71a 100644 > --- a/block/genhd.c > +++ b/block/genhd.c > @@ -772,6 +772,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk, > const struct attribute_group **groups, > bool register_queue) > { > + struct request_queue *q = disk->queue; > dev_t devt; > int retval; > > @@ -782,7 +783,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk, > * registration. > */ > if (register_queue) > - elevator_init_mq(disk->queue); > + elevator_init_mq(q); > > /* minors == 0 indicates to use ext devt from part0 and should > * be accompanied with EXT_DEVT flag. Make sure all > @@ -812,7 +813,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk, > disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; > disk->flags |= GENHD_FL_NO_PART_SCAN; > } else { > - struct backing_dev_info *bdi = disk->queue->backing_dev_info; > + struct backing_dev_info *bdi = q->backing_dev_info; > struct device *dev = disk_to_dev(disk); > int ret; Not sure how/why these changes got here... Not that I care too much :) > > diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c > index 5ca7216e9e01f3..89b33b402b4e52 100644 > --- a/drivers/block/aoe/aoeblk.c > +++ b/drivers/block/aoe/aoeblk.c > @@ -347,7 +347,6 @@ aoeblk_gdalloc(void *vp) > mempool_t *mp; > struct request_queue *q; > struct blk_mq_tag_set *set; > - enum { KB = 1024, MB = KB * KB, READ_AHEAD = 2 * MB, }; > ulong flags; > int late = 0; > int err; > @@ -407,7 +406,6 @@ aoeblk_gdalloc(void *vp) > WARN_ON(d->gd); > WARN_ON(d->flags & DEVFL_UP); > blk_queue_max_hw_sectors(q, BLK_DEF_MAX_SECTORS); > - q->backing_dev_info->ra_pages = READ_AHEAD / PAGE_SIZE; > d->bufpool = mp; > d->blkq = gd->queue = q; > q->queuedata = d; Shouldn't AOE set 2MB optimal IO size so that readahead is equivalent to previous behavior? > diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c > index 1bbdc410ee3c51..ff2101d56cd7f1 100644 > --- a/drivers/md/bcache/super.c > +++ b/drivers/md/bcache/super.c > @@ -1427,10 +1427,6 @@ static int cached_dev_init(struct cached_dev *dc, unsigned int block_size) > if (ret) > return ret; > > - dc->disk.disk->queue->backing_dev_info->ra_pages = > - max(dc->disk.disk->queue->backing_dev_info->ra_pages, > - q->backing_dev_info->ra_pages); > - So bcache is basically stacking readahead here on top of underlying cache device. I don't see this being replicated by your patch so it is lost now? Probably this should be replaced by properly inheriting optimal IO size? Honza -- Jan Kara SUSE Labs, CR