From: tada keisuke <keisuke1.tada@kioxia.com>
To: "song@kernel.org" <song@kernel.org>,
"yukuai3@huawei.com" <yukuai3@huawei.com>
Cc: "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH v2 00/11] md: avoid counter operation conflicts
Date: Thu, 18 Apr 2024 05:43:54 +0000 [thread overview]
Message-ID: <3c0ab8eb94ad4b6fb4cb2159f0638650@kioxia.com> (raw)
Changes in v2:
- Add message of performance in cover.
- Fix a problem of error code initialization in patch 6.
- Fix a problem of sleeping during rcu_read_lock() in patch 9.
- Change base-commit from md-6.9 to md-6.10
Currently, active_aligned_reads and nr_pending used as counters are atomic types.
Therefore, when inc/dec in a multi-core results in conflicts and READ I/O becomes slow.
To improve performance, use "percpu_ref" counters that can avoid conflicts and maintain consistency.
Switch modes of percpu_ref to achieve both consistency and conflict avoidance.
During normal operations such as inc/dec, it operates as percpu mode.
When consistency is required, it operates as atomic mode.
The operations that require consistency are as follows:
- Zero check for the counter
- All operations in RAID 1/10
Patches 1, 3, 6 change active_aligned_reads, and patches 2, 4, 5, 7 to 11 change nr_pending.
nr_pending temporarily switch from percpu mode to atomic mode in patch 7.
This is to reduce the amount of changes from patches 8 to 10.
Finally, nr_pending switch from atomic mode to percpu mode in patch 11.
We applied the patch to base-commit and used fio to compare IOPS.
CPU: AMD EPYC 7313P (3.0GHz, 16cores)
DISK: ramdisk x 3 (modprobe brd rd_nr=3)
RAID: level 5
fio config: bs=4k, rw=randread, iodepth=128, numjobs=16
without patch: 3.64 MIOPS
with patch : 3.84 MIOPS
Keisuke TADA (11):
add infra for active_aligned_reads changes
add infra for nr_pending changes
workaround for inconsistency of config state in takeover
minimize execution of zero check for nr_pending
match the type of variables to percpu_ref
avoid conflicts in active_aligned_reads operations
change the type of nr_pending from atomic_t to percpu_ref
add atomic mode switching in RAID 1/10
add atomic mode switching when removing disk
add atomic mode switching when I/O completion
avoid conflicts in nr_pending operations
drivers/md/md-bitmap.c | 2 +-
drivers/md/md.c | 48 ++++++++++++++++++---
drivers/md/md.h | 62 +++++++++++++++++++++++----
drivers/md/raid1.c | 37 +++++++++++------
drivers/md/raid10.c | 60 ++++++++++++++++-----------
drivers/md/raid5-cache.c | 4 +-
drivers/md/raid5.c | 90 +++++++++++++++++++++++++++-------------
drivers/md/raid5.h | 17 +++++++-
8 files changed, 238 insertions(+), 82 deletions(-)
base-commit: 9d1110f99c253ccef82e480bfe9f38a12eb797a7
--
2.34.1
next reply other threads:[~2024-04-18 6:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 5:43 tada keisuke [this message]
2024-04-18 9:58 ` [PATCH v2 00/11] md: avoid counter operation conflicts Xiao Ni
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