Commit 2004cef1 authored Sep 19, 2024 by Linus Torvalds

Merge tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Implement the SCHED_DEADLINE server infrastructure - Daniel Bristot
   de Oliveira's last major contribution to the kernel:

     "SCHED_DEADLINE servers can help fixing starvation issues of low
      priority tasks (e.g., SCHED_OTHER) when higher priority tasks
      monopolize CPU cycles. Today we have RT Throttling; DEADLINE
      servers should be able to replace and improve that."

   (Daniel Bristot de Oliveira, Peter Zijlstra, Joel Fernandes, Youssef
   Esmat, Huang Shijie)

 - Preparatory changes for sched_ext integration:
     - Use set_next_task(.first) where required
     - Fix up set_next_task() implementations
     - Clean up DL server vs. core sched
     - Split up put_prev_task_balance()
     - Rework pick_next_task()
     - Combine the last put_prev_task() and the first set_next_task()
     - Rework dl_server
     - Add put_prev_task(.next)

   (Peter Zijlstra, with a fix by Tejun Heo)

 - Complete the EEVDF transition and refine EEVDF scheduling:
     - Implement delayed dequeue
     - Allow shorter slices to wakeup-preempt
     - Use sched_attr::sched_runtime to set request/slice suggestion
     - Document the new feature flags
     - Remove unused and duplicate-functionality fields
     - Simplify & unify pick_next_task_fair()
     - Misc debuggability enhancements

   (Peter Zijlstra, with fixes/cleanups by Dietmar Eggemann, Valentin
   Schneider and Chuyi Zhou)

 - Initialize the vruntime of a new task when it is first enqueued,
   resulting in significant decrease in latency of newly woken tasks
   (Zhang Qiao)

 - Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
   (K Prateek Nayak, Peter Zijlstra)

 - Clean up and clarify the usage of Clean up usage of rt_task()
   (Qais Yousef)

 - Preempt SCHED_IDLE entities in strict cgroup hierarchies
   (Tianchen Ding)

 - Clarify the documentation of time units for deadline scheduler
   parameters (Christian Loehle)

 - Remove the HZ_BW chicken-bit feature flag introduced a year ago,
   the original change seems to be working fine (Phil Auld)

 - Misc fixes and cleanups (Chen Yu, Dan Carpenter, Huang Shijie,
   Peilin He, Qais Yousefm and Vincent Guittot)

* tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits)
  sched/cpufreq: Use NSEC_PER_MSEC for deadline task
  cpufreq/cppc: Use NSEC_PER_MSEC for deadline task
  sched/deadline: Clarify nanoseconds in uapi
  sched/deadline: Convert schedtool example to chrt
  sched/debug: Fix the runnable tasks output
  sched: Fix sched_delayed vs sched_core
  kernel/sched: Fix util_est accounting for DELAY_DEQUEUE
  kthread: Fix task state in kthread worker if being frozen
  sched/pelt: Use rq_clock_task() for hw_pressure
  sched/fair: Move effective_cpu_util() and effective_cpu_util() in fair.c
  sched/core: Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
  sched: Add put_prev_task(.next)
  sched: Rework dl_server
  sched: Combine the last put_prev_task() and the first set_next_task()
  sched: Rework pick_next_task()
  sched: Split up put_prev_task_balance()
  sched: Clean up DL server vs core sched
  sched: Fixup set_next_task() implementations
  sched: Use set_next_task(.first) where required
  sched/fair: Properly deactivate sched_delayed task upon class change
  ...

parents 509d2cd1 bc9057da

Documentation/scheduler/sched-deadline.rst

+6 −8

Original line number	Diff line number	Diff line
		@@ -749,21 +749,19 @@ Appendix A. Test suite
		of the command line options. Please refer to rt-app documentation for more
		details (`<rt-app-sources>/doc/*.json`).

		The second testing application is a modification of schedtool, called
		schedtool-dl, which can be used to setup SCHED_DEADLINE parameters for a
		certain pid/application. schedtool-dl is available at:
		https://github.com/scheduler-tools/schedtool-dl.git.
		The second testing application is done using chrt which has support
		for SCHED_DEADLINE.

		The usage is straightforward::

		# schedtool -E -t 10000000:100000000 -e ./my_cpuhog_app
		# chrt -d -T 10000000 -D 100000000 0 ./my_cpuhog_app

		With this, my_cpuhog_app is put to run inside a SCHED_DEADLINE reservation
		of 10ms every 100ms (note that parameters are expressed in microseconds).
		You can also use schedtool to create a reservation for an already running
		of 10ms every 100ms (note that parameters are expressed in nanoseconds).
		You can also use chrt to create a reservation for an already running
		application, given that you know its pid::

		# schedtool -E -t 10000000:100000000 my_app_pid
		# chrt -d -T 10000000 -D 100000000 -p 0 my_app_pid

		Appendix B. Minimal main()
		==========================

drivers/cpufreq/cppc_cpufreq.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -224,9 +224,9 @@ static void __init cppc_freq_invariance_init(void)
		* Fake (unused) bandwidth; workaround to "fix"
		* priority inheritance.
		*/
		.sched_runtime = 1000000,
		.sched_deadline = 10000000,
		.sched_period = 10000000,
		.sched_runtime = NSEC_PER_MSEC,
		.sched_deadline = 10 * NSEC_PER_MSEC,
		.sched_period = 10 * NSEC_PER_MSEC,
		};
		int ret;

fs/bcachefs/six.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -335,7 +335,7 @@ static inline bool six_owner_running(struct six_lock *lock)
		*/
		rcu_read_lock();
		struct task_struct *owner = READ_ONCE(lock->owner);
		bool ret = owner ? owner_on_cpu(owner) : !rt_task(current);
		bool ret = owner ? owner_on_cpu(owner) : !rt_or_dl_task(current);
		rcu_read_unlock();

		return ret;

fs/proc/base.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2626,7 +2626,7 @@ static ssize_t timerslack_ns_write(struct file file, const char __user buf,
		}

		task_lock(p);
		if (task_is_realtime(p))
		if (rt_or_dl_task_policy(p))
		slack_ns = 0;
		else if (slack_ns == 0)
		slack_ns = p->default_timer_slack_ns;

include/linux/ioprio.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -40,7 +40,7 @@ static inline int task_nice_ioclass(struct task_struct *task)
		{
		if (task->policy == SCHED_IDLE)
		return IOPRIO_CLASS_IDLE;
		else if (task_is_realtime(task))
		else if (rt_or_dl_task_policy(task))
		return IOPRIO_CLASS_RT;
		else
		return IOPRIO_CLASS_BE;