mbox series

[md-6.9,v3,00/11] md/raid1: refactor read_balance() and some minor fix

Message ID 20240228114333.527222-1-yukuai1@huaweicloud.com
Headers
Series md/raid1: refactor read_balance() and some minor fix |

Message

Yu Kuai Feb. 28, 2024, 11:43 a.m. UTC 
  From: Yu Kuai <yukuai3@huawei.com>

Changes in v3:
 - add patch 2, and fix that setup_conf() is missing in patch3;
 - add some review tag from Xiao Ni(other than patch 2,3);
Changes in v2:
 - add new conter in conf for patch 2;
 - fix the case choose next idle while there is no other idle disk in
 patch 3;
 - add some review tag from Xiao Ni for patch 1, 4-8

The original idea is that Paul want to optimize raid1 read
performance([1]), however, we think that the original code for
read_balance() is quite complex, and we don't want to add more
complexity. Hence we decide to refactor read_balance() first, to make
code cleaner and easier for follow up.  

Before this patchset, read_balance() has many local variables and many
branches, it want to consider all the scenarios in one iteration. The
idea of this patch is to divide them into 4 different steps:

1) If resync is in progress, find the first usable disk, patch 5;
Otherwise:
2) Loop through all disks and skipping slow disks and disks with bad
blocks, choose the best disk, patch 10. If no disk is found:
3) Look for disks with bad blocks and choose the one with most number of
sectors, patch 8. If no disk is found:
4) Choose first found slow disk with no bad blocks, or slow disk with
most number of sectors, patch 7.

Note that step 3) and step 4) are super code path, and performance
should not be considered.

And after this patchset, we'll continue to optimize read_balance for
step 2), specifically how to choose the best rdev to read.

[1] https://lore.kernel.org/all/20240102125115.129261-1-paul.e.luse@linux.intel.com/

Yu Kuai (11):
  md: add a new helper rdev_has_badblock()
  md/raid1: factor out helpers to add rdev to conf
  md/raid1: record nonrot rdevs while adding/removing rdevs to conf
  md/raid1: fix choose next idle in read_balance()
  md/raid1-10: add a helper raid1_check_read_range()
  md/raid1-10: factor out a new helper raid1_should_read_first()
  md/raid1: factor out read_first_rdev() from read_balance()
  md/raid1: factor out choose_slow_rdev() from read_balance()
  md/raid1: factor out choose_bb_rdev() from read_balance()
  md/raid1: factor out the code to manage sequential IO
  md/raid1: factor out helpers to choose the best rdev from
    read_balance()

 drivers/md/md.h       |  11 +
 drivers/md/raid1-10.c |  69 ++++++
 drivers/md/raid1.c    | 539 +++++++++++++++++++++++++-----------------
 drivers/md/raid1.h    |   1 +
 drivers/md/raid10.c   |  58 ++---
 drivers/md/raid5.c    |  35 +--
 6 files changed, 437 insertions(+), 276 deletions(-)

Comments

Xiao Ni Feb. 28, 2024, 12:35 p.m. UTC | #1 
On Wed, Feb 28, 2024 at 7:49 PM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@huawei.com>
>
> Changes in v3:
>  - add patch 2, and fix that setup_conf() is missing in patch3;
>  - add some review tag from Xiao Ni(other than patch 2,3);
> Changes in v2:
>  - add new conter in conf for patch 2;
>  - fix the case choose next idle while there is no other idle disk in
>  patch 3;
>  - add some review tag from Xiao Ni for patch 1, 4-8
>
> The original idea is that Paul want to optimize raid1 read
> performance([1]), however, we think that the original code for
> read_balance() is quite complex, and we don't want to add more
> complexity. Hence we decide to refactor read_balance() first, to make
> code cleaner and easier for follow up.
>
> Before this patchset, read_balance() has many local variables and many
> branches, it want to consider all the scenarios in one iteration. The
> idea of this patch is to divide them into 4 different steps:
>
> 1) If resync is in progress, find the first usable disk, patch 5;
> Otherwise:
> 2) Loop through all disks and skipping slow disks and disks with bad
> blocks, choose the best disk, patch 10. If no disk is found:
> 3) Look for disks with bad blocks and choose the one with most number of
> sectors, patch 8. If no disk is found:
> 4) Choose first found slow disk with no bad blocks, or slow disk with
> most number of sectors, patch 7.
>
> Note that step 3) and step 4) are super code path, and performance
> should not be considered.
>
> And after this patchset, we'll continue to optimize read_balance for
> step 2), specifically how to choose the best rdev to read.
>
> [1] https://lore.kernel.org/all/20240102125115.129261-1-paul.e.luse@linuxintel.com/
>
> Yu Kuai (11):
>   md: add a new helper rdev_has_badblock()
>   md/raid1: factor out helpers to add rdev to conf
>   md/raid1: record nonrot rdevs while adding/removing rdevs to conf
>   md/raid1: fix choose next idle in read_balance()
>   md/raid1-10: add a helper raid1_check_read_range()
>   md/raid1-10: factor out a new helper raid1_should_read_first()
>   md/raid1: factor out read_first_rdev() from read_balance()
>   md/raid1: factor out choose_slow_rdev() from read_balance()
>   md/raid1: factor out choose_bb_rdev() from read_balance()
>   md/raid1: factor out the code to manage sequential IO
>   md/raid1: factor out helpers to choose the best rdev from
>     read_balance()
>
>  drivers/md/md.h       |  11 +
>  drivers/md/raid1-10.c |  69 ++++++
>  drivers/md/raid1.c    | 539 +++++++++++++++++++++++++-----------------
>  drivers/md/raid1.h    |   1 +
>  drivers/md/raid10.c   |  58 ++---
>  drivers/md/raid5.c    |  35 +--
>  6 files changed, 437 insertions(+), 276 deletions(-)
>
> --
> 2.39.2
>
Hi Kuai
This patch set looks good to me. By the way, have you run mdadm
regression tests?
Reviewed-by: Xiao Ni <xni@redhat.com>
Song Liu Feb. 28, 2024, 9:23 p.m. UTC | #2 
On Wed, Feb 28, 2024 at 3:49 AM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@huawei.com>
>
> Changes in v3:
>  - add patch 2, and fix that setup_conf() is missing in patch3;
>  - add some review tag from Xiao Ni(other than patch 2,3);

It appears that v3 causes mdadm test "01replace" to run forever.
I haven't figured out why, but v2 doesn't seem to have this issue.

Thanks,
Song

> Changes in v2:
>  - add new conter in conf for patch 2;
>  - fix the case choose next idle while there is no other idle disk in
>  patch 3;
>  - add some review tag from Xiao Ni for patch 1, 4-8
>
> The original idea is that Paul want to optimize raid1 read
> performance([1]), however, we think that the original code for
> read_balance() is quite complex, and we don't want to add more
> complexity. Hence we decide to refactor read_balance() first, to make
> code cleaner and easier for follow up.
Yu Kuai Feb. 29, 2024, 1:14 a.m. UTC | #3 
Hi,

在 2024/02/29 5:23, Song Liu 写道:
> On Wed, Feb 28, 2024 at 3:49 AM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>>
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> Changes in v3:
>>   - add patch 2, and fix that setup_conf() is missing in patch3;
>>   - add some review tag from Xiao Ni(other than patch 2,3);
> 
> It appears that v3 causes mdadm test "01replace" to run forever.
> I haven't figured out why, but v2 doesn't seem to have this issue.

I'm running tests while sending this version, and I found that too this
morning. :(

I'll check out what's wrong and update soon.

Thanks,
Kuai

> 
> Thanks,
> Song
> 
>> Changes in v2:
>>   - add new conter in conf for patch 2;
>>   - fix the case choose next idle while there is no other idle disk in
>>   patch 3;
>>   - add some review tag from Xiao Ni for patch 1, 4-8
>>
>> The original idea is that Paul want to optimize raid1 read
>> performance([1]), however, we think that the original code for
>> read_balance() is quite complex, and we don't want to add more
>> complexity. Hence we decide to refactor read_balance() first, to make
>> code cleaner and easier for follow up.
> 
> .
>