[PATCH v3] blk-cgroup: Replace u64 sync with spinlock for iostat update

[tj at kernel.org]

Hello, Waiman.

On Wed, Jul 17, 2024 at 01:37:56PM -0400, Waiman Long wrote:
> bis->sync is still being used in blk_cgroup_bio_start(). Replacing it with a
> global lock may kill performance. We may have to use a per-cpu lock if we
> want to go this route of eliminating bis->sync.

So, the idea is to keep using u64_sync for blkg->iostat_cpu and use
blkg_stat_lock for blkg->iostat. The former is the only one which is updated
in hot path, right?

Thanks.

-- 
tejun