Merge tag 'cgroup-for-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - Yafang Shao added task_get_cgroup1() helper to enable a similar BPF
   helper so that BPF progs can be more useful on cgroup1 hierarchies.
   While cgroup1 is mostly in maintenance mode, this addition is very
   small while having an outsized usefulness for users who are still on
   cgroup1. Yafang also optimized root cgroup list access by making it
   RCU protected in the process.

 - Waiman Long optimized rstat operation leading to substantially lower
   and more consistent lock hold time while flushing the hierarchical
   statistics. As the lock can be acquired briefly in various hot paths,
   this reduction has cascading benefits.

 - Waiman also improved the quality of isolation for cpuset's isolated
   partitions. CPUs which are allocated to isolated partitions are now
   excluded from running unbound work items and cpu_is_isolated() test
   which is used by vmstat and memcg to reduce interference now includes
   cpuset isolated CPUs. While it isn't there yet, the hope is
   eventually reaching parity with the isolation level provided by the
   `isolcpus` boot param but in a dynamic manner.

* tag 'cgroup-for-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Move rcu_head up near the top of cgroup_root
  cgroup/cpuset: Include isolated cpuset CPUs in cpu_is_isolated() check
  cgroup: Avoid false cacheline sharing of read mostly rstat_cpu
  cgroup/rstat: Optimize cgroup_rstat_updated_list()
  cgroup: Fix documentation for cpu.idle
  cgroup/cpuset: Expose cpuset.cpus.isolated
  workqueue: Move workqueue_set_unbound_cpumask() and its helpers inside CONFIG_SYSFS
  cgroup/rstat: Reduce cpu_lock hold time in cgroup_rstat_flush_locked()
  cgroup/cpuset: Take isolated CPUs out of workqueue unbound cpumask
  cgroup/cpuset: Keep track of CPUs in isolated partitions
  selftests/cgroup: Minor code cleanup and reorganization of test_cpuset_prs.sh
  workqueue: Add workqueue_unbound_exclude_cpumask() to exclude CPUs from wq_unbound_cpumask
  selftests: cgroup: Fixes a typo in a comment
  cgroup: Add a new helper for cgroup1 hierarchy
  cgroup: Add annotation for holding namespace_sem in current_cgns_cgroup_from_root()
  cgroup: Eliminate the need for cgroup_mutex in proc_cgroup_show()
  cgroup: Make operations on the cgroup root_list RCU safe
  cgroup: Remove unnecessary list_empty()

1 files changed, 27 insertions, 6 deletions

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 3f85254f3cef2c..09e65312d20c1b 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1093,7 +1093,11 @@ All time durations are in microseconds.
 	A read-write single value file which exists on non-root
 	cgroups.  The default is "100".
 
-	The weight in the range [1, 10000].
+	For non idle groups (cpu.idle = 0), the weight is in the
+	range [1, 10000].
+
+	If the cgroup has been configured to be SCHED_IDLE (cpu.idle = 1),
+	then the weight will show as a 0.
 
   cpu.weight.nice
 	A read-write single value file which exists on non-root
@@ -1157,6 +1161,16 @@ All time durations are in microseconds.
         values similar to the sched_setattr(2). This maximum utilization
         value is used to clamp the task specific maximum utilization clamp.
 
+  cpu.idle
+	A read-write single value file which exists on non-root cgroups.
+	The default is 0.
+
+	This is the cgroup analog of the per-task SCHED_IDLE sched policy.
+	Setting this value to a 1 will make the scheduling policy of the
+	cgroup SCHED_IDLE. The threads inside the cgroup will retain their
+	own relative priorities, but the cgroup itself will be treated as
+	very low priority relative to its peers.
+
 
 
 Memory
@@ -2316,6 +2330,13 @@ Cpuset Interface Files
 	treated to have an implicit value of "cpuset.cpus" in the
 	formation of local partition.
 
+  cpuset.cpus.isolated
+	A read-only and root cgroup only multiple values file.
+
+	This file shows the set of all isolated CPUs used in existing
+	isolated partitions. It will be empty if no isolated partition
+	is created.
+
   cpuset.cpus.partition
 	A read-write single value file which exists on non-root
 	cpuset-enabled cgroups.  This flag is owned by the parent cgroup
@@ -2358,11 +2379,11 @@ Cpuset Interface Files
 	partition or scheduling domain.  The set of exclusive CPUs is
 	determined by the value of its "cpuset.cpus.exclusive.effective".
 
-	When set to "isolated", the CPUs in that partition will
-	be in an isolated state without any load balancing from the
-	scheduler.  Tasks placed in such a partition with multiple
-	CPUs should be carefully distributed and bound to each of the
-	individual CPUs for optimal performance.
+	When set to "isolated", the CPUs in that partition will be in
+	an isolated state without any load balancing from the scheduler
+	and excluded from the unbound workqueues.  Tasks placed in such
+	a partition with multiple CPUs should be carefully distributed
+	and bound to each of the individual CPUs for optimal performance.
 
 	A partition root ("root" or "isolated") can be in one of the
 	two possible states - valid or invalid.  An invalid partition