From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
To: Nishanth Aravamudan <naravamudan@digitalocean.com>,
Julien Desfossez <jdesfossez@digitalocean.com>,
Peter Zijlstra <peterz@infradead.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Vineeth Pillai <viremana@linux.microsoft.com>,
Aaron Lu <aaron.lwe@gmail.com>,
Aubrey Li <aubrey.intel@gmail.com>,
tglx@linutronix.de, linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, torvalds@linux-foundation.org,
fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com,
Phil Auld <pauld@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Mel Gorman <mgorman@techsingularity.net>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
joel@joelfernandes.org, vineeth@bitbyteword.org,
Chen Yu <yu.c.chen@intel.com>,
Christian Brauner <christian.brauner@ubuntu.com>,
Agata Gruza <agata.gruza@intel.com>,
Antonio Gomez Iglesias <antonio.gomez.iglesias@intel.com>,
graf@amazon.com, konrad.wilk@oracle.com, dfaggioli@suse.com,
pjt@google.com, rostedt@goodmis.org, derkling@google.com,
benbjiang@tencent.com,
Alexandre Chartre <alexandre.chartre@oracle.com>,
James.Bottomley@hansenpartnership.com, OWeisse@umich.edu,
Dhaval Giani <dhaval.giani@oracle.com>,
Junaid Shahid <junaids@google.com>,
jsbarnes@google.com, chris.hyser@oracle.com,
Aubrey Li <aubrey.li@linux.intel.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Tim Chen <tim.c.chen@intel.com>
Subject: [PATCH v8 -tip 17/26] sched: Split the cookie and setup per-task cookie on fork
Date: Mon, 19 Oct 2020 21:43:27 -0400 [thread overview]
Message-ID: <20201020014336.2076526-18-joel@joelfernandes.org> (raw)
In-Reply-To: <20201020014336.2076526-1-joel@joelfernandes.org>
In order to prevent interference and clearly support both per-task and CGroup
APIs, split the cookie into 2 and allow it to be set from either per-task, or
CGroup API. The final cookie is the combined value of both and is computed when
the stop-machine executes during a change of cookie.
Also, for the per-task cookie, it will get weird if we use pointers of any
emphemeral objects. For this reason, introduce a refcounted object who's sole
purpose is to assign unique cookie value by way of the object's pointer.
While at it, refactor the CGroup code a bit. Future patches will introduce more
APIs and support.
Tested-by: Julien Desfossez <jdesfossez@digitalocean.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
include/linux/sched.h | 2 +
kernel/sched/core.c | 241 ++++++++++++++++++++++++++++++++++++++++--
kernel/sched/debug.c | 4 +
3 files changed, 236 insertions(+), 11 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index fe6f225bfbf9..c6034c00846a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -688,6 +688,8 @@ struct task_struct {
#ifdef CONFIG_SCHED_CORE
struct rb_node core_node;
unsigned long core_cookie;
+ unsigned long core_task_cookie;
+ unsigned long core_group_cookie;
unsigned int core_occupation;
#endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bab4ea2f5cd8..30a9e4cb5ce1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -346,11 +346,14 @@ void sched_core_put(void)
mutex_unlock(&sched_core_mutex);
}
+static int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2);
+
#else /* !CONFIG_SCHED_CORE */
static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { }
static inline void sched_core_dequeue(struct rq *rq, struct task_struct *p) { }
static bool sched_core_enqueued(struct task_struct *task) { return false; }
+static int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2) { }
#endif /* CONFIG_SCHED_CORE */
@@ -3583,6 +3586,20 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
#endif
#ifdef CONFIG_SCHED_CORE
RB_CLEAR_NODE(&p->core_node);
+
+ /*
+ * Tag child via per-task cookie only if parent is tagged via per-task
+ * cookie. This is independent of, but can be additive to the CGroup tagging.
+ */
+ if (current->core_task_cookie) {
+
+ /* If it is not CLONE_THREAD fork, assign a unique per-task tag. */
+ if (!(clone_flags & CLONE_THREAD)) {
+ return sched_core_share_tasks(p, p);
+ }
+ /* Otherwise share the parent's per-task tag. */
+ return sched_core_share_tasks(p, current);
+ }
#endif
return 0;
}
@@ -9177,6 +9194,217 @@ static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
#endif /* CONFIG_RT_GROUP_SCHED */
#ifdef CONFIG_SCHED_CORE
+/*
+ * A simple wrapper around refcount. An allocated sched_core_cookie's
+ * address is used to compute the cookie of the task.
+ */
+struct sched_core_cookie {
+ refcount_t refcnt;
+};
+
+/*
+ * sched_core_tag_requeue - Common helper for all interfaces to set a cookie.
+ * @p: The task to assign a cookie to.
+ * @cookie: The cookie to assign.
+ * @group: is it a group interface or a per-task interface.
+ *
+ * This function is typically called from a stop-machine handler.
+ */
+void sched_core_tag_requeue(struct task_struct *p, unsigned long cookie, bool group)
+{
+ if (!p)
+ return;
+
+ if (group)
+ p->core_group_cookie = cookie;
+ else
+ p->core_task_cookie = cookie;
+
+ /* Use up half of the cookie's bits for task cookie and remaining for group cookie. */
+ p->core_cookie = (p->core_task_cookie <<
+ (sizeof(unsigned long) * 4)) + p->core_group_cookie;
+
+ if (sched_core_enqueued(p)) {
+ sched_core_dequeue(task_rq(p), p);
+ if (!p->core_task_cookie)
+ return;
+ }
+
+ if (sched_core_enabled(task_rq(p)) &&
+ p->core_cookie && task_on_rq_queued(p))
+ sched_core_enqueue(task_rq(p), p);
+}
+
+/* Per-task interface */
+static unsigned long sched_core_alloc_task_cookie(void)
+{
+ struct sched_core_cookie *ptr =
+ kmalloc(sizeof(struct sched_core_cookie), GFP_KERNEL);
+
+ if (!ptr)
+ return 0;
+ refcount_set(&ptr->refcnt, 1);
+
+ /*
+ * NOTE: sched_core_put() is not done by put_task_cookie(). Instead, it
+ * is done after the stopper runs.
+ */
+ sched_core_get();
+ return (unsigned long)ptr;
+}
+
+static bool sched_core_get_task_cookie(unsigned long cookie)
+{
+ struct sched_core_cookie *ptr = (struct sched_core_cookie *)cookie;
+
+ /*
+ * NOTE: sched_core_put() is not done by put_task_cookie(). Instead, it
+ * is done after the stopper runs.
+ */
+ sched_core_get();
+ return refcount_inc_not_zero(&ptr->refcnt);
+}
+
+static void sched_core_put_task_cookie(unsigned long cookie)
+{
+ struct sched_core_cookie *ptr = (struct sched_core_cookie *)cookie;
+
+ if (refcount_dec_and_test(&ptr->refcnt))
+ kfree(ptr);
+}
+
+struct sched_core_task_write_tag {
+ struct task_struct *tasks[2];
+ unsigned long cookies[2];
+};
+
+/*
+ * Ensure that the task has been requeued. The stopper ensures that the task cannot
+ * be migrated to a different CPU while its core scheduler queue state is being updated.
+ * It also makes sure to requeue a task if it was running actively on another CPU.
+ */
+static int sched_core_task_join_stopper(void *data)
+{
+ struct sched_core_task_write_tag *tag = (struct sched_core_task_write_tag *)data;
+ int i;
+
+ for (i = 0; i < 2; i++)
+ sched_core_tag_requeue(tag->tasks[i], tag->cookies[i], false /* !group */);
+
+ return 0;
+}
+
+static int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2)
+{
+ struct sched_core_task_write_tag wr = {}; /* for stop machine. */
+ bool sched_core_put_after_stopper = false;
+ unsigned long cookie;
+ int ret = -ENOMEM;
+
+ mutex_lock(&sched_core_mutex);
+
+ /*
+ * NOTE: sched_core_get() is done by sched_core_alloc_task_cookie() or
+ * sched_core_put_task_cookie(). However, sched_core_put() is done
+ * by this function *after* the stopper removes the tasks from the
+ * core queue, and not before. This is just to play it safe.
+ */
+ if (t2 == NULL) {
+ if (t1->core_task_cookie) {
+ sched_core_put_task_cookie(t1->core_task_cookie);
+ sched_core_put_after_stopper = true;
+ wr.tasks[0] = t1; /* Keep wr.cookies[0] reset for t1. */
+ }
+ } else if (t1 == t2) {
+ /* Assign a unique per-task cookie solely for t1. */
+
+ cookie = sched_core_alloc_task_cookie();
+ if (!cookie)
+ goto out_unlock;
+
+ if (t1->core_task_cookie) {
+ sched_core_put_task_cookie(t1->core_task_cookie);
+ sched_core_put_after_stopper = true;
+ }
+ wr.tasks[0] = t1;
+ wr.cookies[0] = cookie;
+ } else
+ /*
+ * t1 joining t2
+ * CASE 1:
+ * before 0 0
+ * after new cookie new cookie
+ *
+ * CASE 2:
+ * before X (non-zero) 0
+ * after 0 0
+ *
+ * CASE 3:
+ * before 0 X (non-zero)
+ * after X X
+ *
+ * CASE 4:
+ * before Y (non-zero) X (non-zero)
+ * after X X
+ */
+ if (!t1->core_task_cookie && !t2->core_task_cookie) {
+ /* CASE 1. */
+ cookie = sched_core_alloc_task_cookie();
+ if (!cookie)
+ goto out_unlock;
+
+ /* Add another reference for the other task. */
+ if (!sched_core_get_task_cookie(cookie)) {
+ return -EINVAL;
+ goto out_unlock;
+ }
+
+ wr.tasks[0] = t1;
+ wr.tasks[1] = t2;
+ wr.cookies[0] = wr.cookies[1] = cookie;
+
+ } else if (t1->core_task_cookie && !t2->core_task_cookie) {
+ /* CASE 2. */
+ sched_core_put_task_cookie(t1->core_task_cookie);
+ sched_core_put_after_stopper = true;
+
+ wr.tasks[0] = t1; /* Reset cookie for t1. */
+
+ } else if (!t1->core_task_cookie && t2->core_task_cookie) {
+ /* CASE 3. */
+ if (!sched_core_get_task_cookie(t2->core_task_cookie)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ wr.tasks[0] = t1;
+ wr.cookies[0] = t2->core_task_cookie;
+
+ } else {
+ /* CASE 4. */
+ if (!sched_core_get_task_cookie(t2->core_task_cookie)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ sched_core_put_task_cookie(t1->core_task_cookie);
+ sched_core_put_after_stopper = true;
+
+ wr.tasks[0] = t1;
+ wr.cookies[0] = t2->core_task_cookie;
+ }
+
+ stop_machine(sched_core_task_join_stopper, (void *)&wr, NULL);
+
+ if (sched_core_put_after_stopper)
+ sched_core_put();
+
+ ret = 0;
+out_unlock:
+ mutex_unlock(&sched_core_mutex);
+ return ret;
+}
+
+/* CGroup interface */
static u64 cpu_core_tag_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
{
struct task_group *tg = css_tg(css);
@@ -9207,18 +9435,9 @@ static int __sched_write_tag(void *data)
* when we set cgroup tag to 0 when the loop is done below.
*/
while ((p = css_task_iter_next(&it))) {
- p->core_cookie = !!val ? (unsigned long)tg : 0UL;
-
- if (sched_core_enqueued(p)) {
- sched_core_dequeue(task_rq(p), p);
- if (!p->core_cookie)
- continue;
- }
-
- if (sched_core_enabled(task_rq(p)) &&
- p->core_cookie && task_on_rq_queued(p))
- sched_core_enqueue(task_rq(p), p);
+ unsigned long cookie = !!val ? (unsigned long)tg : 0UL;
+ sched_core_tag_requeue(p, cookie, true /* group */);
}
css_task_iter_end(&it);
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index c8fee8d9dfd4..88bf45267672 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -1024,6 +1024,10 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
__PS("clock-delta", t1-t0);
}
+#ifdef CONFIG_SCHED_CORE
+ __PS("core_cookie", p->core_cookie);
+#endif
+
sched_show_numa(p, m);
}
--
2.29.0.rc1.297.gfa9743e501-goog
next prev parent reply other threads:[~2020-10-20 1:44 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 1:43 [PATCH v8 -tip 00/26] Core scheduling Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 01/26] sched: Wrap rq::lock access Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 02/26] sched: Introduce sched_class::pick_task() Joel Fernandes (Google)
2020-10-22 7:59 ` Li, Aubrey
2020-10-22 15:25 ` Joel Fernandes
2020-10-23 5:25 ` Li, Aubrey
2020-10-23 21:47 ` Joel Fernandes
2020-10-24 2:48 ` Li, Aubrey
2020-10-24 11:10 ` Vineeth Pillai
2020-10-24 12:27 ` Vineeth Pillai
2020-10-24 23:48 ` Li, Aubrey
2020-10-26 9:01 ` Peter Zijlstra
2020-10-27 3:17 ` Li, Aubrey
2020-10-27 14:19 ` Joel Fernandes
2020-10-27 15:23 ` Joel Fernandes
2020-10-27 14:14 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 03/26] sched: Core-wide rq->lock Joel Fernandes (Google)
2020-10-26 11:59 ` Peter Zijlstra
2020-10-27 16:27 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 04/26] sched/fair: Add a few assertions Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 05/26] sched: Basic tracking of matching tasks Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 06/26] sched: Add core wide task selection and scheduling Joel Fernandes (Google)
2020-10-23 13:51 ` Peter Zijlstra
2020-10-23 13:54 ` Peter Zijlstra
2020-10-23 17:57 ` Joel Fernandes
2020-10-23 19:26 ` Peter Zijlstra
2020-10-23 21:31 ` Joel Fernandes
2020-10-26 8:28 ` Peter Zijlstra
2020-10-27 16:58 ` Joel Fernandes
2020-10-26 9:31 ` Peter Zijlstra
2020-11-05 18:50 ` Joel Fernandes
2020-11-05 22:07 ` Joel Fernandes
2020-10-23 15:05 ` Peter Zijlstra
2020-10-23 17:59 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 07/26] sched/fair: Fix forced idle sibling starvation corner case Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 08/26] sched/fair: Snapshot the min_vruntime of CPUs on force idle Joel Fernandes (Google)
2020-10-26 12:47 ` Peter Zijlstra
2020-10-28 15:29 ` Joel Fernandes
2020-10-28 18:39 ` Joel Fernandes
2020-10-29 16:59 ` Joel Fernandes
2020-10-29 18:24 ` Joel Fernandes
2020-10-29 18:59 ` Peter Zijlstra
2020-10-30 2:36 ` Joel Fernandes
2020-10-30 2:42 ` Joel Fernandes
2020-10-30 8:41 ` Peter Zijlstra
2020-10-31 21:41 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 09/26] sched: Trivial forced-newidle balancer Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 10/26] sched: migration changes for core scheduling Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 11/26] irq_work: Cleanup Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 12/26] arch/x86: Add a new TIF flag for untrusted tasks Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 13/26] kernel/entry: Add support for core-wide protection of kernel-mode Joel Fernandes (Google)
2020-10-20 3:41 ` Randy Dunlap
2020-11-03 0:20 ` Joel Fernandes
2020-10-22 5:48 ` Li, Aubrey
2020-11-03 0:50 ` Joel Fernandes
2020-10-30 10:29 ` Alexandre Chartre
2020-11-03 1:20 ` Joel Fernandes
2020-11-06 16:57 ` Alexandre Chartre
2020-11-06 17:43 ` Joel Fernandes
2020-11-06 18:07 ` Alexandre Chartre
2020-11-10 9:35 ` Alexandre Chartre
2020-11-10 22:42 ` Joel Fernandes
2020-11-16 10:08 ` Alexandre Chartre
2020-11-16 14:50 ` Joel Fernandes
2020-11-16 15:43 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 14/26] entry/idle: Enter and exit kernel protection during idle entry and exit Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 15/26] entry/kvm: Protect the kernel when entering from guest Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 16/26] sched: cgroup tagging interface for core scheduling Joel Fernandes (Google)
2020-10-20 1:43 ` Joel Fernandes (Google) [this message]
2020-11-04 22:30 ` [PATCH v8 -tip 17/26] sched: Split the cookie and setup per-task cookie on fork chris hyser
2020-11-05 14:49 ` Joel Fernandes
2020-11-09 23:30 ` chris hyser
2020-10-20 1:43 ` [PATCH v8 -tip 18/26] sched: Add a per-thread core scheduling interface Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 19/26] sched: Add a second-level tag for nested CGroup usecase Joel Fernandes (Google)
2020-10-31 0:42 ` Josh Don
2020-11-03 2:54 ` Joel Fernandes
[not found] ` <6c07e70d-52f2-69ff-e1fa-690cd2c97f3d@linux.intel.com>
2020-11-05 15:52 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 20/26] sched: Release references to the per-task cookie on exit Joel Fernandes (Google)
2020-11-04 21:50 ` chris hyser
2020-11-05 15:46 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 21/26] sched: Handle task addition to CGroup Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 22/26] sched/debug: Add CGroup node for printing group cookie if SCHED_DEBUG Joel Fernandes (Google)
2020-10-20 1:43 ` [PATCH v8 -tip 23/26] kselftest: Add tests for core-sched interface Joel Fernandes (Google)
2020-10-30 22:20 ` [PATCH] sched: Change all 4 space tabs to actual tabs John B. Wyatt IV
2020-10-20 1:43 ` [PATCH v8 -tip 24/26] sched: Move core-scheduler interfacing code to a new file Joel Fernandes (Google)
2020-10-26 1:05 ` Li, Aubrey
2020-11-03 2:58 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 25/26] Documentation: Add core scheduling documentation Joel Fernandes (Google)
2020-10-20 3:36 ` Randy Dunlap
2020-11-12 16:11 ` Joel Fernandes
2020-10-20 1:43 ` [PATCH v8 -tip 26/26] sched: Debug bits Joel Fernandes (Google)
2020-10-30 13:26 ` [PATCH v8 -tip 00/26] Core scheduling Ning, Hongyu
2020-11-06 2:58 ` Li, Aubrey
2020-11-06 17:54 ` Joel Fernandes
2020-11-09 6:04 ` Li, Aubrey
2020-11-06 20:55 ` [RFT for v9] (Was Re: [PATCH v8 -tip 00/26] Core scheduling) Joel Fernandes
2020-11-13 9:22 ` Ning, Hongyu
2020-11-13 10:01 ` Ning, Hongyu
[not found] <4ff7f030-b797-6711-fb6a-fe39bb02075a@oracle.com>
2020-11-09 23:23 ` [PATCH v8 -tip 17/26] sched: Split the cookie and setup per-task cookie on fork chris hyser
2020-11-10 14:15 ` Joel Fernandes
2020-11-17 0:45 ` Joel Fernandes
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