[v6,0/3] blk-cgroup: Optimize blkcg_rstat_flush()

Message

Waiman Long June 2, 2022, 7:20 p.m. UTC

v6:
  - Add a missing free_percpu() into blkcg_css_free() in patch 3.
  - Integrating the documentation patch 4 back into patch 3.

 v5:
  - Add a new patch 2 to eliminate the use of intermediate "ret"
    variable in blkcg_css_alloc() to fix compilation warning reported
    by kernel test robot.

 v4:
  - Update comment and eliminate "inline" keywords as suggested by TJ.

 v3:
  - Update comments in patch 2.
  - Put rcu_read_lock/unlock() in blkcg_rstat_flush().
  - Use READ_ONCE/WRITE_ONCE() to access lnode->next to reduce data
    races.
  - Get a blkg reference when putting into the lockless list and put it
    back when removed.
 
This patch series improves blkcg_rstat_flush() performance by eliminating
unnecessary blkg enumeration and flush operations for those blkg's and
blkg_iostat_set's that haven't been updated since the last flush.

Waiman Long (3):
  blk-cgroup: Correctly free percpu iostat_cpu in blkg on error exit
  blk-cgroup: Return -ENOMEM directly in blkcg_css_alloc() error path
  blk-cgroup: Optimize blkcg_rstat_flush()

 block/blk-cgroup.c | 119 +++++++++++++++++++++++++++++++++++++++------
 block/blk-cgroup.h |   9 ++++
 2 files changed, 112 insertions(+), 16 deletions(-)