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
