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Groups > linux.kernel > #1628295
| From | Waiman Long <longman@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [RFC PATCH 04/14] cgroup: implement CSS_TASK_ITER_THREADED |
| Date | 2017-04-21 16:10 +0200 |
| Message-ID | <tyHq3-6LU-49@gated-at.bofh.it> (permalink) |
| References | <tyHq1-6LU-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
From: Tejun Heo <tj@kernel.org>
cgroup v2 is in the process of growing thread granularity support.
Once thread mode is enabled, the root cgroup of the subtree serves as
the proc_cgrp to which the processes of the subtree conceptually
belong and domain-level resource consumptions not tied to any specific
task are charged. In the subtree, threads won't be subject to process
granularity or no-internal-task constraint and can be distributed
arbitrarily across the subtree.
This patch implements a new task iterator flag CSS_TASK_ITER_THREADED,
which, when used on a proc_cgrp, makes the iteration include the tasks
on all the associated threaded css_sets. "cgroup.procs" read path is
updated to use it so that reading the file on a proc_cgrp lists all
processes. This will also be used by controller implementations which
need to walk processes or tasks at the resource domain level.
Task iteration is implemented nested in css_set iteration. If
CSS_TASK_ITER_THREADED is specified, after walking tasks of each
!threaded css_set, all the associated threaded css_sets are visited
before moving onto the next !threaded css_set.
Signed-off-by: Tejun Heo <tj@kernel.org>
---
include/linux/cgroup.h | 6 ++++
kernel/cgroup/cgroup.c | 81 +++++++++++++++++++++++++++++++++++++++++---------
2 files changed, 73 insertions(+), 14 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 37b20ef..d62d75c 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -38,6 +38,8 @@
/* walk only threadgroup leaders */
#define CSS_TASK_ITER_PROCS (1U << 0)
+/* walk threaded css_sets as part of their proc_csets */
+#define CSS_TASK_ITER_THREADED (1U << 1)
/* a css_task_iter should be treated as an opaque object */
struct css_task_iter {
@@ -47,11 +49,15 @@ struct css_task_iter {
struct list_head *cset_pos;
struct list_head *cset_head;
+ struct list_head *tcset_pos;
+ struct list_head *tcset_head;
+
struct list_head *task_pos;
struct list_head *tasks_head;
struct list_head *mg_tasks_head;
struct css_set *cur_cset;
+ struct css_set *cur_pcset;
struct task_struct *cur_task;
struct list_head iters_node; /* css_set->task_iters */
};
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 016bbc6..b2b1886 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3592,27 +3592,36 @@ bool css_has_online_children(struct cgroup_subsys_state *css)
return ret;
}
-/**
- * css_task_iter_advance_css_set - advance a task itererator to the next css_set
- * @it: the iterator to advance
- *
- * Advance @it to the next css_set to walk.
- */
-static void css_task_iter_advance_css_set(struct css_task_iter *it)
+static struct css_set *css_task_iter_next_css_set(struct css_task_iter *it)
{
- struct list_head *l = it->cset_pos;
+ bool threaded = it->flags & CSS_TASK_ITER_THREADED;
+ struct list_head *l;
struct cgrp_cset_link *link;
struct css_set *cset;
lockdep_assert_held(&css_set_lock);
- /* Advance to the next non-empty css_set */
+ /* find the next threaded cset */
+ if (it->tcset_pos) {
+ l = it->tcset_pos->next;
+
+ if (l != it->tcset_head) {
+ it->tcset_pos = l;
+ return container_of(l, struct css_set,
+ threaded_csets_node);
+ }
+
+ it->tcset_pos = NULL;
+ }
+
+ /* find the next cset */
+ l = it->cset_pos;
+
do {
l = l->next;
if (l == it->cset_head) {
it->cset_pos = NULL;
- it->task_pos = NULL;
- return;
+ return NULL;
}
if (it->ss) {
@@ -3622,10 +3631,50 @@ static void css_task_iter_advance_css_set(struct css_task_iter *it)
link = list_entry(l, struct cgrp_cset_link, cset_link);
cset = link->cset;
}
- } while (!css_set_populated(cset));
+
+ /*
+ * For threaded iterations, threaded csets are walked
+ * together with their proc_csets. Skip here.
+ */
+ } while (threaded && css_set_threaded(cset));
it->cset_pos = l;
+ /* initialize threaded cset walking */
+ if (threaded) {
+ if (it->cur_pcset)
+ put_css_set_locked(it->cur_pcset);
+ it->cur_pcset = cset;
+ get_css_set(cset);
+
+ it->tcset_head = &cset->threaded_csets;
+ it->tcset_pos = &cset->threaded_csets;
+ }
+
+ return cset;
+}
+
+/**
+ * css_task_iter_advance_css_set - advance a task itererator to the next css_set
+ * @it: the iterator to advance
+ *
+ * Advance @it to the next css_set to walk.
+ */
+static void css_task_iter_advance_css_set(struct css_task_iter *it)
+{
+ struct css_set *cset;
+
+ lockdep_assert_held(&css_set_lock);
+
+ /* Advance to the next non-empty css_set */
+ do {
+ cset = css_task_iter_next_css_set(it);
+ if (!cset) {
+ it->task_pos = NULL;
+ return;
+ }
+ } while (!css_set_populated(cset));
+
if (!list_empty(&cset->tasks))
it->task_pos = cset->tasks.next;
else
@@ -3768,6 +3817,9 @@ void css_task_iter_end(struct css_task_iter *it)
spin_unlock_irq(&css_set_lock);
}
+ if (it->cur_pcset)
+ put_css_set(it->cur_pcset);
+
if (it->cur_task)
put_task_struct(it->cur_task);
}
@@ -3793,6 +3845,7 @@ static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
struct kernfs_open_file *of = s->private;
struct cgroup *cgrp = seq_css(s)->cgroup;
struct css_task_iter *it = of->priv;
+ unsigned iter_flags = CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED;
/*
* When a seq_file is seeked, it's always traversed sequentially
@@ -3806,10 +3859,10 @@ static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
if (!it)
return ERR_PTR(-ENOMEM);
of->priv = it;
- css_task_iter_start(&cgrp->self, CSS_TASK_ITER_PROCS, it);
+ css_task_iter_start(&cgrp->self, iter_flags, it);
} else if (!(*pos)++) {
css_task_iter_end(it);
- css_task_iter_start(&cgrp->self, CSS_TASK_ITER_PROCS, it);
+ css_task_iter_start(&cgrp->self, iter_flags, it);
}
return cgroup_procs_next(s, NULL, NULL);
--
1.8.3.1
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[RFC PATCH 00/14] cgroup: Implement cgroup v2 thread mode & CPU controller Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 08/14] cgroup: Keep accurate count of tasks in each css_set Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 12/14] sched: Implement interface for cgroup unified hierarchy Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 13/14] sched: Make cpu/cpuacct threaded controllers Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 03/14] cgroup: introduce cgroup->proc_cgrp and threaded css_set handling Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 09/14] cgroup: Make debug cgroup support v2 and thread mode Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 06/14] cgroup: Fix reference counting bug in cgroup_procs_write() Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 07/14] cgroup: Move debug cgroup to its own file Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 05/14] cgroup: implement cgroup v2 thread support Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 10/14] cgroup: Implement new thread mode semantics Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 04/14] cgroup: implement CSS_TASK_ITER_THREADED Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 14/14] cgroup: Enable separate control knobs for thread root internal processes Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 02/14] cgroup: add @flags to css_task_iter_start() and implement CSS_TASK_ITER_PROCS Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 11/14] sched: Misc preps for cgroup unified hierarchy interface Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200 [RFC PATCH 01/14] cgroup: reorganize cgroup.procs / task write path Waiman Long <longman@redhat.com> - 2017-04-21 16:10 +0200
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