linux-kernel - Re: [PATCH v10 0/3] blk-cgroup: Optimize blkcg_rstat

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Message-ID: <4b5142be-6a47-9dfd-a238-5b9d29b296b8@redhat.com>
Date:   Wed, 16 Nov 2022 18:06:13 -0500
From:   Waiman Long <longman@...hat.com>
To:     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>,
        Michal Koutný <mkoutny@...e.com>,
        Hillf Danton <hdanton@...a.com>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v10 0/3] blk-cgroup: Optimize blkcg_rstat_flush()

On 11/4/22 20:58, Waiman Long wrote:
>   v10:
>    - Update patch 3 to rename the rstat function to
>      cgroup_rstat_css_cpu_flush().
>
>   v9:
>    - Remove patch "llist: Allow optional sentinel node terminated lockless
>      list" for now. This will be done as a follow-up patch.
>    - Add a new lqueued field to blkg_iostat_set to store the status of
>      whether lnode is in a lockless list.
>    - Add a new patch 3 to speed up the freeing of blkcg by flushing out
>      the rstat lockless lists at blkcg offline time.
>
>   v8:
>    - Update the llist patch to make existing llist functions and macros
>      work for both NULL and sentinel terminated lockless list as much
>      as possible and leave only the initialization and removal functions
>      to have a sentinel terminated llist variants.
>
> 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: Return -ENOMEM directly in blkcg_css_alloc() error path
>    blk-cgroup: Optimize blkcg_rstat_flush()
>    blk-cgroup: Flush stats at blkgs destruction path
>
>   block/blk-cgroup.c     | 103 +++++++++++++++++++++++++++++++++++------
>   block/blk-cgroup.h     |  10 ++++
>   include/linux/cgroup.h |   1 +
>   kernel/cgroup/rstat.c  |  20 ++++++++
>   4 files changed, 119 insertions(+), 15 deletions(-)

Jens, do you have any further comment on this patchset? Is it possible 
to queue it for the next Linux version?

Cheers,
Longman