Re: [PATCH 07/13] block: lift setting the readahead size into the block layer

Coly Li
2020-09-22T09:51:52Z

On 2020/9/21 16:07, 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 <hch@lst.de>
> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

For the bcache part,

Acked-by: Coly Li <colyli@suse.de>

Thanks.

Coly Li

> ---
> block/blk-settings.c | 5 ++---
> block/blk-sysfs.c | 9 +++++++++
> drivers/block/aoe/aoeblk.c | 1 -
> drivers/block/drbd/drbd_nl.c | 12 +-----------
> drivers/md/bcache/super.c | 3 ---
> drivers/md/raid0.c | 16 ----------------
> drivers/md/raid10.c | 24 +-----------------------
> drivers/md/raid5.c | 13 +------------
> 8 files changed, 14 insertions(+), 69 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..83915b4a1fc3ad 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -854,6 +854,15 @@ 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/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
> index d8cfc233e64b93..c34e71b0c4a98c 100644
> --- a/drivers/block/aoe/aoeblk.c
> +++ b/drivers/block/aoe/aoeblk.c
> @@ -406,7 +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 = SZ_2M / PAGE_SIZE;
> blk_queue_io_opt(q, SZ_2M);
> d->bufpool = mp;
> d->blkq = gd->queue = q;
> diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
> index aaff5bde391506..f8fb1c9b1bb6c1 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 48113005ed86ad..6bfa771673623e 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1427,9 +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);
> blk_queue_io_opt(dc->disk.disk->queue,
> max(queue_io_opt(dc->disk.disk->queue), queue_io_opt(q)));
>
> 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 9956a04ac13bd6..5d1bdee313ec33 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -3873,19 +3873,6 @@ 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;
>
> @@ -4723,17 +4710,8 @@ 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 9a7d1250894ef1..7ace1f76b14736 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -7522,8 +7522,6 @@ 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);
> @@ -8111,17 +8109,8 @@ 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);
> - }
> }
> }
>
>