On 7/8/24 14:45, Tejun Heo wrote:
Hello, Waiman.
On Fri, Jul 05, 2024 at 08:56:21PM -0400, Waiman Long wrote:
The /proc/cgroups file shows the number of cgroups for each of the
subsystems. With cgroup v1, the number of CSSes is the same as the
number of cgroups. That is not the case anymore with cgroup v2. The
/proc/cgroups file cannot show the actual number of CSSes for the
subsystems that are bound to cgroup v2.
So if a v2 cgroup subsystem is leaking cgroups (typically memory
cgroup), we can't tell by looking at /proc/cgroups which cgroup
subsystems may be responsible. This patch adds a css counter in the
cgroup_subsys structure to keep track of the number of CSSes for each
of the cgroup subsystems.
The count sounds useful to me but can we add it in cgroup.stats instead?
That information is certainly useful to display to cgroup.stat which
currently only shows nr_descendants and nr_dying_descendants. So does
"nr_<subsys_name> <cnt>" for each cgroup subsystems look good to you or
do you have other suggestion?
The reason for this patch is because I got a bug report about leaking
blkio cgroup due to the information shown in /proc/cgroups. I know you
want do deprecate it for cgroup v2. How about adding a iine like "#
Deprecated for cgroup v2, use cgroup.stats file for cgroup counts" at
the top of /proc/cgroups when cgroup v2 is active?
Cheers,
Longman
