[ANNOUNCE] Nohz cpusets (adaptive tickless kernel) v2-pre-20120308

[ANNOUNCE] Nohz cpusets (adaptive tickless kernel) v2-pre-20120308

[Frederic Weisbecker]

Hi everyone,

Reminder of what it's all about: https://lkml.org/lkml/2011/8/15/245

The whole patchset has moved forward enough that it's now time
to release a new iteration of it. I plan to post all the patches
soon to LKML but before that I would like to rebase against 3.3[-rc >= 6]
and clean up a few little things, especially revisit some changelogs.

So before that to happen, I still wanted to do a release in order
to keep everyone in touch with latest changes.

Latest changes can be found at:

git://github.com/fweisbec/linux-dynticks.git
	nohz/cpuset-v2-pre-20120308

There is still a lot to do, but I'm glad we made some progresses with
more idle/adaptive tickless code unification, namespace cleanups,
RCU fixes, and various bugfixes here and there, etc...

Changes since v1 (https://lkml.org/lkml/2011/8/15/245):

- Rebase against latest Paul McKenney's rcu/core branch for v3.3-rc1

- Adapt against latest rcu changes: introduce new APIs
  rcu_user_enter(), rcu_user_exit(), rcu_user_enter_irq()
  and rcu_user_exit_irq()

- Handle RCU idle mode with do_notify_resume() path

- Fix deadlock after double rq lock on schedule:
	schedule() -> rq_lock -> next is idle task ->
	tick_nohz_restart_sched_tick() -> wake up softirq ->
	rq lock

- Fix lockup while issuing flush times IPI on exit path:

	CPU 0				CPU 1

	read_lock(tasklist_lock)
					write_lock_irq(tasklist_lock)
	smp_call_function(CPU 1)
	* deadlock *

- Many namespace renames (cpuset_* to tick_nohz_*) and code migration
from sched.c to tick-sched.c

- Seperate code that determine if we can stop the idle tick and don't
use it for adaptive tickless mode.

- Fix adaptive tickless mode set on idle incidentally. TIF_NOHZ was
then missing on the following task that ran tickless, issuing some
illegal uses of RCU

- Restart the tick anytime more than one task is on the runqueue. We were previously
only covering wake ups, now we also handle migration and any other source of task enqueuing

- Handle use of RCU in schedule() when called right before resuming userspace
(new schedule_user() API)

- Take the decision to stop the tick from irq exit instead of the middle of the timer
interrupt. This gives more opportunity to stop it and is one step more to unify idle
and adaptive tickless.

- Unify tickless idle and tickless user/system CPU time accounting infrastructures.

- If the tick is stopped adaptively and we are going to schedule the idle
task, don't restart the tick.

- Remove task_nohz_mode per cpu var and use ts->tick_stopped instead. This
leads to more unification between idle tickless and adaptive tickless.

Have fun!

Re: [ANNOUNCE] Nohz cpusets (adaptive tickless kernel) v2-pre-20120308

[Frederic Weisbecker]

On Thu, Mar 08, 2012 at 03:57:40AM +0100, Frederic Weisbecker wrote:
> Hi everyone,
> 
> Reminder of what it's all about: https://lkml.org/lkml/2011/8/15/245
> 
> The whole patchset has moved forward enough that it's now time
> to release a new iteration of it. I plan to post all the patches
> soon to LKML but before that I would like to rebase against 3.3[-rc >= 6]
> and clean up a few little things, especially revisit some changelogs.
> 
> So before that to happen, I still wanted to do a release in order
> to keep everyone in touch with latest changes.
> 
> Latest changes can be found at:
> 
> git://github.com/fweisbec/linux-dynticks.git
> 	nohz/cpuset-v2-pre-20120308
> 
> There is still a lot to do, but I'm glad we made some progresses with
> more idle/adaptive tickless code unification, namespace cleanups,
> RCU fixes, and various bugfixes here and there, etc...
> 
> Changes since v1 (https://lkml.org/lkml/2011/8/15/245):
> 
> - Rebase against latest Paul McKenney's rcu/core branch for v3.3-rc1
> 
> - Adapt against latest rcu changes: introduce new APIs
>   rcu_user_enter(), rcu_user_exit(), rcu_user_enter_irq()
>   and rcu_user_exit_irq()
> 
> - Handle RCU idle mode with do_notify_resume() path
> 
> - Fix deadlock after double rq lock on schedule:
> 	schedule() -> rq_lock -> next is idle task ->
> 	tick_nohz_restart_sched_tick() -> wake up softirq ->
> 	rq lock
> 
> - Fix lockup while issuing flush times IPI on exit path:
> 
> 	CPU 0				CPU 1
> 
> 	read_lock(tasklist_lock)
> 					write_lock_irq(tasklist_lock)
> 	smp_call_function(CPU 1)
> 	* deadlock *
> 
> - Many namespace renames (cpuset_* to tick_nohz_*) and code migration
> from sched.c to tick-sched.c
> 
> - Seperate code that determine if we can stop the idle tick and don't
> use it for adaptive tickless mode.
> 
> - Fix adaptive tickless mode set on idle incidentally. TIF_NOHZ was
> then missing on the following task that ran tickless, issuing some
> illegal uses of RCU
> 
> - Restart the tick anytime more than one task is on the runqueue. We were previously
> only covering wake ups, now we also handle migration and any other source of task enqueuing
> 
> - Handle use of RCU in schedule() when called right before resuming userspace
> (new schedule_user() API)
> 
> - Take the decision to stop the tick from irq exit instead of the middle of the timer
> interrupt. This gives more opportunity to stop it and is one step more to unify idle
> and adaptive tickless.
> 
> - Unify tickless idle and tickless user/system CPU time accounting infrastructures.
> 
> - If the tick is stopped adaptively and we are going to schedule the idle
> task, don't restart the tick.
> 
> - Remove task_nohz_mode per cpu var and use ts->tick_stopped instead. This
> leads to more unification between idle tickless and adaptive tickless.
> 
> Have fun!


Frederic Weisbecker (34):
      nohz: Drop useless call in tick_nohz_start_idle()
      nohz: Drop useless ts->inidle checks on idle exit
      nohz: Separate idle sleeping time accounting from nohz switching
      nohz: Move idle ticks stats tracking out of nohz handlers
      nohz: Rename ts->idle_tick to ts->last_tick
      nohz: Move nohz load balancer selection into idle logic
      nohz: Move ts->idle_calls into strict idle logic
      nohz: Move next idle expiring time record into idle logic area
      cpuset: Set up interface for nohz flag
      nohz: Try not to give the timekeeping duty to a cpuset nohz cpu
      x86: New cpuset nohz irq vector
      nohz: Adaptive tick stop and restart on nohz cpuset
      nohz/cpuset: Don't turn off the tick if rcu needs it
      nohz/cpuset: Wake up adaptive nohz CPU when a timer gets enqueued
      nohz/cpuset: Don't stop the tick if posix cpu timers are running
      nohz/cpuset: Restart tick when nohz flag is cleared on cpuset
      nohz/cpuset: Restart the tick if printk needs it
      rcu: Restart the tick on non-responding adaptive nohz CPUs
      rcu: Restart tick if we enqueue a callback in a nohz/cpuset CPU
      nohz: Generalize tickless cpu time accounting
      nohz/cpuset: Account user and system times in adaptive nohz mode
      nohz/cpuset: New API to flush cputimes on nohz cpusets
      nohz/cpuset: Flush cputime on threads in nohz cpusets when waiting leader
      nohz/cpuset: Flush cputimes on procfs stat file read
      nohz/cpuset: Flush cputimes for getrusage() and times() syscalls
      x86: Syscall hooks for nohz cpusets
      x86: Exception hooks for nohz cpusets
      x86: Add adaptive tickless hooks on do_notify_resume()
      nohz: Don't restart the tick before scheduling to idle
      rcu: New rcu_user_enter() and rcu_user_exit() APIs
      rcu: New rcu_user_enter_irq() and rcu_user_exit_irq() APIs
      rcu: Switch to extended quiescent state in userspace from nohz cpuset
      nohz: Exit RCU idle mode when we schedule before resuming userspace
      nohz/cpuset: Disable under some configs

---
 arch/Kconfig                       |    3 +
 arch/x86/Kconfig                   |    1 +
 arch/x86/include/asm/entry_arch.h  |    3 +
 arch/x86/include/asm/hw_irq.h      |    7 +
 arch/x86/include/asm/irq_vectors.h |    2 +
 arch/x86/include/asm/smp.h         |   11 +
 arch/x86/include/asm/thread_info.h |   10 +-
 arch/x86/kernel/entry_64.S         |   14 +-
 arch/x86/kernel/irqinit.c          |    4 +
 arch/x86/kernel/ptrace.c           |   10 +
 arch/x86/kernel/signal.c           |    3 +
 arch/x86/kernel/smp.c              |   26 ++
 arch/x86/kernel/traps.c            |   22 +-
 arch/x86/mm/fault.c                |   13 +-
 fs/proc/array.c                    |    2 +
 include/linux/cpuset.h             |   26 ++
 include/linux/kernel_stat.h        |    2 +
 include/linux/posix-timers.h       |    1 +
 include/linux/rcupdate.h           |    8 +
 include/linux/sched.h              |   10 +-
 include/linux/tick.h               |   76 ++++--
 init/Kconfig                       |    8 +
 kernel/cpuset.c                    |  105 +++++++
 kernel/exit.c                      |    8 +
 kernel/posix-cpu-timers.c          |   12 +
 kernel/printk.c                    |   15 +-
 kernel/rcutree.c                   |  156 ++++++++---
 kernel/sched.c                     |   98 +++++++-
 kernel/softirq.c                   |    5 +-
 kernel/sys.c                       |    6 +
 kernel/time/tick-sched.c           |  534 ++++++++++++++++++++++++++++--------
 kernel/time/timer_list.c           |    7 +-
 kernel/timer.c                     |    2 +-
 33 files changed, 1018 insertions(+), 192 deletions(-)