user/sven/linux.git/include/linux/tick.h, branch v3.17

nohz: Restore NMI safe local irq work for local nohz kick

2014-09-04T20:35:59Z

The local nohz kick is currently used by perf which needs it to be NMI-safe. Recent commit though (7d1311b93e58ed55f3a31cc8f94c4b8fe988a2b9) changed its implementation to fire the local kick using the remote kick API. It was convenient to make the code more generic but the remote kick isn't NMI-safe. As a result: WARNING: CPU: 3 PID: 18062 at kernel/irq_work.c:72 irq_work_queue_on+0x11e/0x140() CPU: 3 PID: 18062 Comm: trinity-subchil Not tainted 3.16.0+ #34 0000000000000009 00000000903774d1 ffff880244e06c00 ffffffff9a7f1e37 0000000000000000 ffff880244e06c38 ffffffff9a0791dd ffff880244fce180 0000000000000003 ffff880244e06d58 ffff880244e06ef8 0000000000000000 Call Trace: [] dump_stack+0x4e/0x7a [] warn_slowpath_common+0x7d/0xa0 [] warn_slowpath_null+0x1a/0x20 [] irq_work_queue_on+0x11e/0x140 [] tick_nohz_full_kick_cpu+0x57/0x90 [] __perf_event_overflow+0x275/0x350 [] ? perf_event_task_disable+0xa0/0xa0 [] ? x86_perf_event_set_period+0xbf/0x150 [] perf_event_overflow+0x14/0x20 [] intel_pmu_handle_irq+0x206/0x410 [] ? arch_vtime_task_switch+0x63/0x130 [] perf_event_nmi_handler+0x2b/0x50 [] nmi_handle+0xd2/0x390 [] ? nmi_handle+0x5/0x390 [] ? lock_release+0xab/0x330 [] default_do_nmi+0x72/0x1c0 [] ? cpuacct_account_field+0xcf/0x200 [] do_nmi+0xb8/0x100 Lets fix this by restoring the use of local irq work for the nohz local kick. Reported-by: Catalin Iacob Reported-and-tested-by: Dave Jones Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Frederic Weisbecker

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-08-04T23:23:30Z

Pull scheduler updates from Ingo Molnar: - Move the nohz kick code out of the scheduler tick to a dedicated IPI, from Frederic Weisbecker. This necessiated quite some background infrastructure rework, including: * Clean up some irq-work internals * Implement remote irq-work * Implement nohz kick on top of remote irq-work * Move full dynticks timer enqueue notification to new kick * Move multi-task notification to new kick * Remove unecessary barriers on multi-task notification - Remove proliferation of wait_on_bit() action functions and allow wait_on_bit_action() functions to support a timeout. (Neil Brown) - Another round of sched/numa improvements, cleanups and fixes. (Rik van Riel) - Implement fast idling of CPUs when the system is partially loaded, for better scalability. (Tim Chen) - Restructure and fix the CPU hotplug handling code that may leave cfs_rq and rt_rq's throttled when tasks are migrated away from a dead cpu. (Kirill Tkhai) - Robustify the sched topology setup code. (Peterz Zijlstra) - Improve sched_feat() handling wrt. static_keys (Jason Baron) - Misc fixes. * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits) sched/fair: Fix 'make xmldocs' warning caused by missing description sched: Use macro for magic number of -1 for setparam sched: Robustify topology setup sched: Fix sched_setparam() policy == -1 logic sched: Allow wait_on_bit_action() functions to support a timeout sched: Remove proliferation of wait_on_bit() action functions sched/numa: Revert "Use effective_load() to balance NUMA loads" sched: Fix static_key race with sched_feat() sched: Remove extra static_key*() function indirection sched/rt: Fix replenish_dl_entity() comments to match the current upstream code sched: Transform resched_task() into resched_curr() sched/deadline: Kill task_struct->pi_top_task sched: Rework check_for_tasks() sched/rt: Enqueue just unthrottled rt_rq back on the stack in __disable_runtime() sched/fair: Disable runtime_enabled on dying rq sched/numa: Change scan period code to match intent sched/numa: Rework best node setting in task_numa_migrate() sched/numa: Examine a task move when examining a task swap sched/numa: Simplify task_numa_compare() sched/numa: Use effective_load() to balance NUMA loads ...

rcu: Bind grace-period kthreads to non-NO_HZ_FULL CPUs

2014-07-09T16:15:02Z

Binding the grace-period kthreads to the timekeeping CPU resulted in significant performance decreases for some workloads. For more detail, see: https://lkml.org/lkml/2014/6/3/395 for benchmark numbers https://lkml.org/lkml/2014/6/4/218 for CPU statistics It turns out that it is necessary to bind the grace-period kthreads to the timekeeping CPU only when all but CPU 0 is a nohz_full CPU on the one hand or if CONFIG_NO_HZ_FULL_SYSIDLE=y on the other. In other cases, it suffices to bind the grace-period kthreads to the set of non-nohz_full CPUs. This commit therefore creates a tick_nohz_not_full_mask that is the complement of tick_nohz_full_mask, and then binds the grace-period kthread to the set of CPUs indicated by this new mask, which covers the CONFIG_NO_HZ_FULL_SYSIDLE=n case. The CONFIG_NO_HZ_FULL_SYSIDLE=y case still binds the grace-period kthreads to the timekeeping CPU. This commit also includes the tick_nohz_full_enabled() check suggested by Frederic Weisbecker. Reported-by: Jet Chen Signed-off-by: Paul E. McKenney [ paulmck: Created housekeeping_affine() and housekeeping_mask per fweisbec feedback. ]

nohz: Support nohz full remote kick

2014-06-16T14:26:54Z

Remotely kicking a full nohz CPU in order to make it re-evaluate its next tick is currently implemented using the scheduler IPI. However this bloats a scheduler fast path with an off-topic feature. The scheduler tick was abused here for its cool "callable anywhere/anytime" properties. But now that the irq work subsystem can queue remote callbacks, it's a perfect fit to safely queue IPIs when interrupts are disabled without worrying about concurrent callers. So lets implement remote kick on top of irq work. This is going to be used when a new event requires the next tick to be recalculated: more than 1 task competing on the CPU, timer armed, ... Acked-by: Peter Zijlstra Cc: Andrew Morton Cc: Ingo Molnar Cc: Kevin Hilman Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Viresh Kumar Signed-off-by: Frederic Weisbecker

tick: Rename tick_check_idle() to tick_irq_enter()

2014-01-15T22:05:31Z

This makes the code more symetric against the existing tick functions called on irq exit: tick_irq_exit() and tick_nohz_irq_exit(). These function are also symetric as they mirror each other's action: we start to account idle time on irq exit and we stop this accounting on irq entry. Also the tick is stopped on irq exit and timekeeping catches up with the tickless time elapsed until we reach irq entry. This rename was suggested by Peter Zijlstra a long while ago but it got forgotten in the mass. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Alex Shi Cc: Steven Rostedt Cc: Paul E. McKenney Cc: John Stultz Cc: Kevin Hilman Link: http://lkml.kernel.org/r/1387320692-28460-2-git-send-email-fweisbec@gmail.com Signed-off-by: Frederic Weisbecker

context_tracking: Wrap static key check into more intuitive function name

2013-12-02T19:43:14Z

Use a function with a meaningful name to check the global context tracking state. static_key_false() is a bit confusing for reviewers. Signed-off-by: Frederic Weisbecker Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Oleg Nesterov Cc: Steven Rostedt

nohz: Convert a few places to use local per cpu accesses

2013-12-02T19:39:30Z

A few functions use remote per CPU access APIs when they deal with local values. Just do the right conversion to improve performance, code readability and debug checks. While at it, lets extend some of these function names with *_this_cpu() suffix in order to display their purpose more clearly. Signed-off-by: Frederic Weisbecker Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Oleg Nesterov Cc: Steven Rostedt

Merge branch 'timers/nohz-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/nohz

2013-08-14T15:58:56Z

Pull nohz improvements from Frederic Weisbecker: " It mostly contains fixes and full dynticks off-case optimizations. I believe that distros want to enable this feature so it seems important to optimize the case where the "nohz_full=" parameter is empty. ie: I'm trying to remove any performance regression that comes with NO_HZ_FULL=y when the feature is not used. This patchset improves the current situation a lot (off-case appears to be around 11% faster with hackbench, although I guess it may vary depending on the configuration but it should be significantly faster in any case) now there is still some work to do: I can still observe a remaining loss of 1.6% throughput seen with hackbench compared to CONFIG_NO_HZ_FULL=n. " Signed-off-by: Ingo Molnar

nohz: Optimize full dynticks's sched hooks with static keys

2013-08-14T15:14:58Z

Scheduler IPIs and task context switches are serious fast path. Let's try to hide as much as we can the impact of full dynticks APIs' off case that are called on these sites through the use of static keys. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman

nohz: Optimize full dynticks state checks with static keys

2013-08-14T15:14:57Z

These APIs are frequenctly accessed and priority is given to optimize the full dynticks off-case in order to let distros enable this feature without suffering from significant performance regressions. Let's inline these APIs and optimize them with static keys. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman