From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH 06/14] block: lift setting the readahead size into the block layer Date: Wed, 26 Aug 2020 18:07:38 -0400 Message-ID: <20200826220737.GA25613@redhat.com> References: <20200726150333.305527-1-hch@lst.de> <20200726150333.305527-7-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200726150333.305527-7-hch@lst.de> Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig Cc: Jens Axboe , linux-raid@vger.kernel.org, Hans de Goede , Minchan Kim , Richard Weinberger , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Song Liu , dm-devel@redhat.com, linux-mtd@lists.infradead.org, cgroups@vger.kernel.org, drbd-dev@tron.linbit.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, martin.petersen@oracle.com List-Id: dm-devel.ids On Sun, Jul 26 2020 at 11:03am -0400, 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 | 1 - > block/genhd.c | 13 +++++++++++-- > 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, 16 insertions(+), 77 deletions(-) In general these changes need a solid audit relative to stacking drivers. That is, the limits stacking methods (blk_stack_limits) vs lower level allocation methods (__device_add_disk). You optimized for lowlevel __device_add_disk establishing the bdi's ra_pages and io_pages. That is at the beginning of disk allocation, well before any build up of stacking driver's queue_io_opt() -- which was previously done in disk_stack_limits or driver specific methods (e.g. dm_table_set_restrictions) that are called _after_ all the limits stacking occurs. By inverting the setting of the bdi's ra_pages and io_pages to be done so early in __device_add_disk it'll break properly setting these values for at least DM afaict. Mike > 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 7dda709f3ccb6f..ce418d9128a0b2 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); > > return ret; > diff --git a/block/genhd.c b/block/genhd.c > index 8b1e9f48957cb5..097d4e4bc0b8a2 100644 > --- a/block/genhd.c > +++ b/block/genhd.c > @@ -775,6 +775,7 @@ 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; > > @@ -785,7 +786,7 @@ 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 > @@ -815,10 +816,18 @@ 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; > > + /* > + * For read-ahead of large files to be effective, we need to > + * readahead at least twice the optimal I/O size. > + */ > + bdi->ra_pages = max(queue_io_opt(q) * 2 / PAGE_SIZE, > + VM_READAHEAD_PAGES); > + bdi->io_pages = queue_max_sectors(q) >> (PAGE_SHIFT - 9); > + > /* Register BDI before referencing it from bdev */ > dev->devt = devt; > ret = bdi_register(bdi, "%u:%u", MAJOR(devt), MINOR(devt)); > 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; > diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c > index 650372ee2c7822..212bf711fb6b41 100644 > --- a/drivers/block/drbd/drbd_nl.c > +++ b/drivers/block/drbd/drbd_nl.c > @@ -1360,18 +1360,8 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi > decide_on_discard_support(device, q, b, discard_zeroes_if_aligned); > decide_on_write_same_support(device, q, b, o, disable_write_same); > > - if (b) { > + if (b) > blk_stack_limits(&q->limits, &b->limits, 0); > - > - if (q->backing_dev_info->ra_pages != > - b->backing_dev_info->ra_pages) { > - drbd_info(device, "Adjusting my ra_pages to backing device's (%lu -> %lu)\n", > - q->backing_dev_info->ra_pages, > - b->backing_dev_info->ra_pages); > - q->backing_dev_info->ra_pages = > - b->backing_dev_info->ra_pages; > - } > - } > fixup_discard_if_not_supported(q); > fixup_write_zeroes(device, q); > } > diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c > index 9e45faa054b6f4..9d3f0711be030f 100644 > --- a/drivers/md/bcache/super.c > +++ b/drivers/md/bcache/super.c > @@ -1367,10 +1367,6 @@ 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); > - > atomic_set(&dc->io_errors, 0); > dc->io_disable = false; > dc->error_limit = DEFAULT_CACHED_DEV_ERROR_LIMIT; > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c > index aac4c31cfc8498..324a42ed2f8894 100644 > --- a/drivers/md/dm-table.c > +++ b/drivers/md/dm-table.c > @@ -1924,9 +1924,6 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q, > q->nr_zones = blkdev_nr_zones(t->md->disk); > } > #endif > - > - /* Allow reads to exceed readahead limits */ > - q->backing_dev_info->io_pages = limits->max_sectors >> (PAGE_SHIFT - 9); > } > > unsigned int dm_table_get_num_targets(struct dm_table *t) > diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c > index f54a449f97aa79..aa2d7279176880 100644 > --- a/drivers/md/raid0.c > +++ b/drivers/md/raid0.c > @@ -410,22 +410,6 @@ static int raid0_run(struct mddev *mddev) > mdname(mddev), > (unsigned long long)mddev->array_sectors); > > - if (mddev->queue) { > - /* calculate the max read-ahead size. > - * For read-ahead of large files to be effective, we need to > - * readahead at least twice a whole stripe. i.e. number of devices > - * multiplied by chunk size times 2. > - * If an individual device has an ra_pages greater than the > - * chunk size, then we will not drive that device as hard as it > - * wants. We consider this a configuration error: a larger > - * chunksize should be used in that case. > - */ > - int stripe = mddev->raid_disks * > - (mddev->chunk_sectors << 9) / PAGE_SIZE; > - if (mddev->queue->backing_dev_info->ra_pages < 2* stripe) > - mddev->queue->backing_dev_info->ra_pages = 2* stripe; > - } > - > dump_zones(mddev); > > ret = md_integrity_register(mddev); > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c > index 9f88ff9bdee437..23d15acbf457d4 100644 > --- a/drivers/md/raid10.c > +++ b/drivers/md/raid10.c > @@ -3865,19 +3865,6 @@ static int raid10_run(struct mddev *mddev) > mddev->resync_max_sectors = size; > set_bit(MD_FAILFAST_SUPPORTED, &mddev->flags); > > - if (mddev->queue) { > - int stripe = conf->geo.raid_disks * > - ((mddev->chunk_sectors << 9) / PAGE_SIZE); > - > - /* Calculate max read-ahead size. > - * We need to readahead at least twice a whole stripe.... > - * maybe... > - */ > - stripe /= conf->geo.near_copies; > - if (mddev->queue->backing_dev_info->ra_pages < 2 * stripe) > - mddev->queue->backing_dev_info->ra_pages = 2 * stripe; > - } > - > if (md_integrity_register(mddev)) > goto out_free_conf; > > @@ -4715,17 +4702,8 @@ static void end_reshape(struct r10conf *conf) > conf->reshape_safe = MaxSector; > spin_unlock_irq(&conf->device_lock); > > - /* read-ahead size must cover two whole stripes, which is > - * 2 * (datadisks) * chunksize where 'n' is the number of raid devices > - */ > - if (conf->mddev->queue) { > - int stripe = conf->geo.raid_disks * > - ((conf->mddev->chunk_sectors << 9) / PAGE_SIZE); > - stripe /= conf->geo.near_copies; > - if (conf->mddev->queue->backing_dev_info->ra_pages < 2 * stripe) > - conf->mddev->queue->backing_dev_info->ra_pages = 2 * stripe; > + if (conf->mddev->queue) > raid10_set_io_opt(conf); > - } > conf->fullsync = 0; > } > > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c > index 68e41ce3ca75cc..415ce3cc155698 100644 > --- a/drivers/md/raid5.c > +++ b/drivers/md/raid5.c > @@ -7413,8 +7413,6 @@ static int raid5_run(struct mddev *mddev) > int data_disks = conf->previous_raid_disks - conf->max_degraded; > int stripe = data_disks * > ((mddev->chunk_sectors << 9) / PAGE_SIZE); > - if (mddev->queue->backing_dev_info->ra_pages < 2 * stripe) > - mddev->queue->backing_dev_info->ra_pages = 2 * stripe; > > chunk_size = mddev->chunk_sectors << 9; > blk_queue_io_min(mddev->queue, chunk_size); > @@ -8002,17 +8000,8 @@ static void end_reshape(struct r5conf *conf) > spin_unlock_irq(&conf->device_lock); > wake_up(&conf->wait_for_overlap); > > - /* read-ahead size must cover two whole stripes, which is > - * 2 * (datadisks) * chunksize where 'n' is the number of raid devices > - */ > - if (conf->mddev->queue) { > - int data_disks = conf->raid_disks - conf->max_degraded; > - int stripe = data_disks * ((conf->chunk_sectors << 9) > - / PAGE_SIZE); > - if (conf->mddev->queue->backing_dev_info->ra_pages < 2 * stripe) > - conf->mddev->queue->backing_dev_info->ra_pages = 2 * stripe; > + if (conf->mddev->queue) > raid5_set_io_opt(conf); > - } > } > } > > -- > 2.27.0 > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel