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Date: Wed, 28 Feb 2024 10:40:06 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Xiao Ni <xni@...hat.com>, Yu Kuai <yukuai1@...weicloud.com>
Cc: paul.e.luse@...ux.intel.com, song@...nel.org, shli@...com,
neilb@...e.com, linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
yi.zhang@...wei.com, yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH md-6.9 v2 02/10] md/raid1: record nonrot rdevs while
adding/removing rdevs to conf
Hi,
在 2024/02/28 9:56, Xiao Ni 写道:
> On Tue, Feb 27, 2024 at 8:09 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>>
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> 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@...ux.intel.com>
>> Signed-off-by: Paul Luse <paul.e.luse@...ux.intel.com>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>> 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?
Yes, it's right. I'll add a helper raid1_add_conf(raid1_info, rdev) and
raid1_remove_conf(raid1_info, rdev) to do this, make sure all the places
to modify conf is covered.
Thanks,
Kuai
>
> 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
>>
>
> .
>
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