On Tue, Feb 27, 2024 at 8:09 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:
>
> From: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> For raid1, each read will iterate all the rdevs from conf and check if
> any rdev is non-rotational, then choose rdev with minimal IO inflight
> if so, or rdev with closest distance otherwise.
>
> Disk nonrot info can be changed through sysfs entry:
>
> /sys/block/[disk_name]/queue/rotational
>
> However, consider that this should only be used for testing, and user
> really shouldn't do this in real life. Record the number of non-rotational
> disks in conf, to avoid checking each rdev in IO fast path and simplify
> read_balance() a little bit.
>
> Co-developed-by: Paul Luse <paul.e.luse@xxxxxxxxxxxxxxx>
> Signed-off-by: Paul Luse <paul.e.luse@xxxxxxxxxxxxxxx>
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ---
> drivers/md/md.h | 1 +
> drivers/md/raid1.c | 17 ++++++++++-------
> drivers/md/raid1.h | 1 +
> 3 files changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index a49ab04ab707..b2076a165c10 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -207,6 +207,7 @@ enum flag_bits {
> * check if there is collision between raid1
> * serial bios.
> */
> + Nonrot, /* non-rotational device (SSD) */
> };
>
> static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index a145fe48b9ce..0fed01b06de9 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -599,7 +599,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
> int sectors;
> int best_good_sectors;
> int best_disk, best_dist_disk, best_pending_disk;
> - int has_nonrot_disk;
> int disk;
> sector_t best_dist;
> unsigned int min_pending;
> @@ -620,7 +619,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
> best_pending_disk = -1;
> min_pending = UINT_MAX;
> best_good_sectors = 0;
> - has_nonrot_disk = 0;
> choose_next_idle = 0;
> clear_bit(R1BIO_FailFast, &r1_bio->state);
>
> @@ -637,7 +635,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
> sector_t first_bad;
> int bad_sectors;
> unsigned int pending;
> - bool nonrot;
>
> rdev = conf->mirrors[disk].rdev;
> if (r1_bio->bios[disk] == IO_BLOCKED
> @@ -703,8 +700,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
> /* At least two disks to choose from so failfast is OK */
> set_bit(R1BIO_FailFast, &r1_bio->state);
>
> - nonrot = bdev_nonrot(rdev->bdev);
> - has_nonrot_disk |= nonrot;
> pending = atomic_read(&rdev->nr_pending);
> dist = abs(this_sector - conf->mirrors[disk].head_position);
> if (choose_first) {
> @@ -731,7 +726,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
> * small, but not a big deal since when the second disk
> * starts IO, the first disk is likely still busy.
> */
> - if (nonrot && opt_iosize > 0 &&
> + if (test_bit(Nonrot, &rdev->flags) && opt_iosize > 0 &&
> mirror->seq_start != MaxSector &&
> mirror->next_seq_sect > opt_iosize &&
> mirror->next_seq_sect - opt_iosize >=
> @@ -763,7 +758,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
> * mixed ratation/non-rotational disks depending on workload.
> */
> if (best_disk == -1) {
> - if (has_nonrot_disk || min_pending == 0)
> + if (READ_ONCE(conf->nonrot_disks) || min_pending == 0)
> best_disk = best_pending_disk;
> else
> best_disk = best_dist_disk;
> @@ -1819,6 +1814,11 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
> WRITE_ONCE(p[conf->raid_disks].rdev, rdev);
> }
>
> + if (!err && bdev_nonrot(rdev->bdev)) {
> + set_bit(Nonrot, &rdev->flags);
> + WRITE_ONCE(conf->nonrot_disks, conf->nonrot_disks + 1);
> + }
> +
Hi Kuai
I noticed raid1_run->setup_conf is used to add rdev to conf when
creating raid1. raid1_add_disk is only used for --add/--re-add after
creating array. So we need to add the same logic in setup_conf?
Regards
Xiao
> print_conf(conf);
> return err;
> }
> @@ -1883,6 +1883,9 @@ static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
> }
> abort:
>
> + if (test_and_clear_bit(Nonrot, &rdev->flags))
> + WRITE_ONCE(conf->nonrot_disks, conf->nonrot_disks - 1);
> +
> print_conf(conf);
> return err;
> }
> diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
> index 14d4211a123a..5300cbaa58a4 100644
> --- a/drivers/md/raid1.h
> +++ b/drivers/md/raid1.h
> @@ -71,6 +71,7 @@ struct r1conf {
> * allow for replacements.
> */
> int raid_disks;
> + int nonrot_disks;
>
> spinlock_t device_lock;
>
> --
> 2.39.2
>
