lkml.org 
[lkml]   [2024]   [May]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] blk-cgroup: Properly propagate the iostat update up the hierarchy
On Wed, May 15, 2024 at 10:30:59AM -0400, Waiman Long wrote:
> During a cgroup_rstat_flush() call, the lowest level of nodes are flushed
> first before their parents. Since commit 3b8cc6298724 ("blk-cgroup:
> Optimize blkcg_rstat_flush()"), iostat propagation was still done to
> the parent. Grandparent, however, may not get the iostat update if the
> parent has no blkg_iostat_set queued in its lhead lockless list.
>
> Fix this iostat propagation problem by queuing the parent's global
> blkg->iostat into one of its percpu lockless lists to make sure that
> the delta will always be propagated up to the grandparent and so on
> toward the root blkcg.
>
> Note that successive calls to __blkcg_rstat_flush() are serialized by
> the cgroup_rstat_lock. So no special barrier is used in the reading
> and writing of blkg->iostat.lqueued.
>
> Fixes: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()")
> Reported-by: Dan Schatzberg <schatzberg.dan@gmail.com>
> Closes: https://lore.kernel.org/lkml/ZkO6l%2FODzadSgdhC@dschatzberg-fedora-PF3DHTBV/
> Signed-off-by: Waiman Long <longman@redhat.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

--
tejun

\
 
 \ /
  Last update: 2024-05-27 18:28    [W:0.036 / U:0.428 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site