linux-kernel - [PATCH v7 0/3] blk-cgroup: Optimize blkcg_rstat

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Message-Id: <20221003154459.207538-1-longman@redhat.com>
Date:   Mon,  3 Oct 2022 11:44:56 -0400
From:   Waiman Long <longman@...hat.com>
To:     Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>
Cc:     cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ming Lei <ming.lei@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Huang Ying <ying.huang@...el.com>,
        Michal Koutný <mkoutny@...e.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v7 0/3] blk-cgroup: Optimize blkcg_rstat_flush()

 v7:
  - Drop patch 1 ("blk-cgroup: Correctly free percpu iostat_cpu in blkg
    on error exit") as it is found to be unnecessary.
  - Add a new llist patch to provide a lockless list variant terminated
    by a sentinel node.
  - Modified patch 3 to use the new sllist API and move percpu_ref_put()
    later in the blkcg_rstat_flush() loop to prevent potential
    use-after-free problem.

 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.

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):
  llist: Add a lock-less list variant terminated by a sentinel node
  blk-cgroup: Return -ENOMEM directly in blkcg_css_alloc() error path
  blk-cgroup: Optimize blkcg_rstat_flush()

 block/blk-cgroup.c    |  85 ++++++++++++++++++++++-----
 block/blk-cgroup.h    |   9 +++
 include/linux/llist.h | 132 +++++++++++++++++++++++++++++++++++++++++-
 lib/llist.c           |  79 ++++++++++++++++++++++++-
 4 files changed, 289 insertions(+), 16 deletions(-)

-- 
2.31.1