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* sched/idle: Conditionally handle tick broadcast in default_idle_call()Thomas Gleixner2024-03-011-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | The x86 architecture has an idle routine for AMD CPUs which are affected by erratum 400. On the affected CPUs the local APIC timer stops in the C1E halt state. It therefore requires tick broadcasting. The invocation of tick_broadcast_enter()/exit() from this function violates the RCU constraints because it can end up in lockdep or tracing, which rightfully triggers a warning. tick_broadcast_enter()/exit() must be invoked before ct_cpuidle_enter() and after ct_cpuidle_exit() in default_idle_call(). Add a static branch conditional invocation of tick_broadcast_enter()/exit() into this function to allow X86 to replace the AMD specific idle code. It's guarded by a config switch which will be selected by x86. Otherwise it's a NOOP. Reported-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20240229142248.266708822@linutronix.de
* clocksource: Loosen clocksource watchdog constraintsPaul E. McKenney2023-01-041-1/+5
| | | | | | | | | | | | | | | | | | | | Currently, MAX_SKEW_USEC is set to 100 microseconds, which has worked reasonably well. However, NTP is willing to tolerate 500 microseconds of skew per second, and a clocksource that is good enough for NTP should be good enough for the clocksource watchdog. The watchdog's skew is controlled by MAX_SKEW_USEC and the CLOCKSOURCE_WATCHDOG_MAX_SKEW_US Kconfig option. However, these values are doubled before being associated with a clocksource's ->uncertainty_margin, and the ->uncertainty_margin values of the pair of clocksource's being compared are summed before checking against the skew. Therefore, set both MAX_SKEW_USEC and the default for the CLOCKSOURCE_WATCHDOG_MAX_SKEW_US Kconfig option to 125 microseconds of skew per second, resulting in 500 microseconds of skew per second in the clocksource watchdog's skew comparison. Suggested-by Rik van Riel <riel@surriel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* context_tracking: Take idle eqs entrypoints over RCUFrederic Weisbecker2022-07-051-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | The RCU dynticks counter is going to be merged into the context tracking subsystem. Start with moving the idle extended quiescent states entrypoints to context tracking. For now those are dumb redirections to existing RCU calls. [ paulmck: Apply kernel test robot feedback. ] Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com> Cc: Uladzislau Rezki <uladzislau.rezki@sony.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com> Cc: Yu Liao <liaoyu15@huawei.com> Cc: Phil Auld <pauld@redhat.com> Cc: Paul Gortmaker<paul.gortmaker@windriver.com> Cc: Alex Belits <abelits@marvell.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
* context_tracking: Split user tracking KconfigFrederic Weisbecker2022-06-301-11/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | Context tracking is going to be used not only to track user transitions but also idle/IRQs/NMIs. The user tracking part will then become a separate feature. Prepare Kconfig for that. [ frederic: Apply Max Filippov feedback. ] Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com> Cc: Uladzislau Rezki <uladzislau.rezki@sony.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com> Cc: Yu Liao <liaoyu15@huawei.com> Cc: Phil Auld <pauld@redhat.com> Cc: Paul Gortmaker<paul.gortmaker@windriver.com> Cc: Alex Belits <abelits@marvell.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
* clocksource: Add a Kconfig option for WATCHDOG_MAX_SKEWWaiman Long2022-02-021-0/+9
| | | | | | | | | | | A watchdog maximum skew of 100us may still be too small for some systems or archs. It may also be too small when some kernel debug config options are enabled. So add a new Kconfig option CLOCKSOURCE_WATCHDOG_MAX_SKEW_US to allow kernel builders to have more control on the threshold for marking clocksource as unstable. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* Merge tag 'timers-core-2021-06-29' of ↵Linus Torvalds2021-06-291-0/+9
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer updates from Thomas Gleixner: "Time and clocksource/clockevent related updates: Core changes: - Infrastructure to support per CPU "broadcast" devices for per CPU clockevent devices which stop in deep idle states. This allows us to utilize the more efficient architected timer on certain ARM SoCs for normal operation instead of permanentely using the slow to access SoC specific clockevent device. - Print the name of the broadcast/wakeup device in /proc/timer_list - Make the clocksource watchdog more robust against delays between reading the current active clocksource and the watchdog clocksource. Such delays can be caused by NMIs, SMIs and vCPU preemption. Handle this by reading the watchdog clocksource twice, i.e. before and after reading the current active clocksource. In case that the two watchdog reads shows an excessive time delta, the read sequence is repeated up to 3 times. - Improve the debug output and add a test module for the watchdog mechanism. - Reimplementation of the venerable time64_to_tm() function with a faster and significantly smaller version. Straight from the source, i.e. the author of the related research paper contributed this! Driver changes: - No new drivers, not even new device tree bindings! - Fixes, improvements and cleanups and all over the place" * tag 'timers-core-2021-06-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (30 commits) time/kunit: Add missing MODULE_LICENSE() time: Improve performance of time64_to_tm() clockevents: Use list_move() instead of list_del()/list_add() clocksource: Print deviation in nanoseconds when a clocksource becomes unstable clocksource: Provide kernel module to test clocksource watchdog clocksource: Reduce clocksource-skew threshold clocksource: Limit number of CPUs checked for clock synchronization clocksource: Check per-CPU clock synchronization when marked unstable clocksource: Retry clock read if long delays detected clockevents: Add missing parameter documentation clocksource/drivers/timer-ti-dm: Drop unnecessary restore clocksource/arm_arch_timer: Improve Allwinner A64 timer workaround clocksource/drivers/arm_global_timer: Remove duplicated argument in arm_global_timer clocksource/drivers/arm_global_timer: Make symbol 'gt_clk_rate_change_nb' static arm: zynq: don't disable CONFIG_ARM_GLOBAL_TIMER due to CONFIG_CPU_FREQ anymore clocksource/drivers/arm_global_timer: Implement rate compensation whenever source clock changes clocksource/drivers/ingenic: Rename unreasonable array names clocksource/drivers/timer-ti-dm: Save and restore timer TIOCP_CFG clocksource/drivers/mediatek: Ack and disable interrupts on suspend clocksource/drivers/samsung_pwm: Constify source IO memory ...
| * time: Improve performance of time64_to_tm()Cassio Neri2021-06-241-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current implementation of time64_to_tm() contains unnecessary loops, branches and look-up tables. The new one uses an arithmetic-based algorithm appeared in [1] and is approximately 3x faster (YMMV). The drawback is that the new code isn't intuitive and contains many 'magic numbers' (not unusual for this type of algorithm). However, [1] justifies all those numbers and, given this function's history, the code is unlikely to need much maintenance, if any at all. Add a KUnit test for it which checks every day in a 160,000 years interval centered at 1970-01-01 against the expected result. [1] Neri, Schneider, "Euclidean Affine Functions and Applications to Calendar Algorithms". https://arxiv.org/abs/2102.06959 Signed-off-by: Cassio Neri <cassio.neri@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210622213616.313046-1-cassio.neri@gmail.com
* | tick/nohz: Update nohz_full Kconfig helpFrederic Weisbecker2021-05-131-5/+6
|/ | | | | | | | | | CONFIG_NO_HZ_FULL behaves just like CONFIG_NO_HZ_IDLE by default. Reassure distros about it. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20210512232924.150322-6-frederic@kernel.org
* Merge tag 'timers-urgent-2020-12-27' of ↵Linus Torvalds2020-12-271-1/+1
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer fixes from Ingo Molnar: "Update/fix two CPU sanity checks in the hotplug and the boot code, and fix a typo in the Kconfig help text. [ Context: the first two commits are the result of an ongoing annotation+review work of (intentional) tick_do_timer_cpu() data races reported by KCSAN, but the annotations aren't fully cooked yet ]" * tag 'timers-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill" tick/sched: Remove bogus boot "safety" check tick: Remove pointless cpu valid check in hotplug code
| * timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill"Colin Ian King2020-12-181-1/+1
| | | | | | | | | | | | | | | | | | | | There is a spelling mistake in the Kconfig help text. Fix it. Signed-off-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Linus Walleij <linus.walleij@linaro.org> Link: https://lore.kernel.org/r/20201217171705.57586-1-colin.king@canonical.com
* | timekeeping: default GENERIC_CLOCKEVENTS to enabledArnd Bergmann2020-10-301-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Almost all machines use GENERIC_CLOCKEVENTS, so it feels wrong to require each one to select that symbol manually. Instead, enable it whenever CONFIG_LEGACY_TIMER_TICK is disabled as a simplification. It should be possible to select both GENERIC_CLOCKEVENTS and LEGACY_TIMER_TICK from an architecture now and decide at runtime between the two. For the clockevents arch-support.txt file, this means that additional architectures are marked as TODO when they have at least one machine that still uses LEGACY_TIMER_TICK, rather than being marked 'ok' when at least one machine has been converted. This means that both m68k and arm (for riscpc) revert to TODO. At this point, we could just always enable CONFIG_GENERIC_CLOCKEVENTS rather than leaving it off when not needed. I built an m68k defconfig kernel (using gcc-10.1.0) and found that this would add around 5.5KB in kernel image size: text data bss dec hex filename 3861936 1092236 196656 5150828 4e986c obj-m68k/vmlinux-no-clockevent 3866201 1093832 196184 5156217 4ead79 obj-m68k/vmlinux-clockevent On Arm (MACH_RPC), that difference appears to be twice as large, around 11KB on top of an 6MB vmlinux. Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Tested-by: Geert Uytterhoeven <geert@linux-m68k.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
* | timekeeping: add CONFIG_LEGACY_TIMER_TICKArnd Bergmann2020-10-301-0/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | All platforms that currently do not use generic clockevents roughly call the same set of functions in their timer interrupts: xtime_update(), update_process_times() and profile_tick(), sometimes in a different sequence. Add a helper function that performs all three of them, to make the callers more uniform and simplify the interface. Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
* | timekeeping: remove arch_gettimeoffsetArnd Bergmann2020-10-301-9/+0
|/ | | | | | | | | With Arm EBSA110 gone, nothing uses it any more, so the corresponding code and the Kconfig option can be removed. Acked-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
* posix-cpu-timers: Provide mechanisms to defer timer handling to task_workThomas Gleixner2020-08-061-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Running posix CPU timers in hard interrupt context has a few downsides: - For PREEMPT_RT it cannot work as the expiry code needs to take sighand lock, which is a 'sleeping spinlock' in RT. The original RT approach of offloading the posix CPU timer handling into a high priority thread was clumsy and provided no real benefit in general. - For fine grained accounting it's just wrong to run this in context of the timer interrupt because that way a process specific CPU time is accounted to the timer interrupt. - Long running timer interrupts caused by a large amount of expiring timers which can be created and armed by unpriviledged user space. There is no hard requirement to expire them in interrupt context. If the signal is targeted at the task itself then it won't be delivered before the task returns to user space anyway. If the signal is targeted at a supervisor process then it might be slightly delayed, but posix CPU timers are inaccurate anyway due to the fact that they are tied to the tick. Provide infrastructure to schedule task work which allows splitting the posix CPU timer code into a quick check in interrupt context and a thread context expiry and signal delivery function. This has to be enabled by architectures as it requires that the architecture specific KVM implementation handles pending task work before exiting to guest mode. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20200730102337.783470146@linutronix.de
* treewide: Add SPDX license identifier - Makefile/KconfigThomas Gleixner2019-05-211-0/+1
| | | | | | | | | | | | | | Add SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any form These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* time: Move CONTEXT_TRACKING to kernel/time/KconfigPaul E. McKenney2019-01-151-0/+29
| | | | | | | | | | | | | | | | Both CONTEXT_TRACKING and CONTEXT_TRACKING_FORCE are currently defined in kernel/rcu/kconfig, which might have made sense at some point, but no longer does given that RCU refers to neither of these Kconfig options. Therefore move them to kernel/time/Kconfig, where the rest of the NO_HZ_FULL Kconfig options live. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: https://lkml.kernel.org/r/20181220170525.GA12579@linux.ibm.com
* clocksource: Provide clocksource_arch_init()Thomas Gleixner2018-10-041-0/+4
| | | | | | | | | | | | | | | | | | | | | | | Architectures have extra archdata in the clocksource, e.g. for VDSO support. There are no sanity checks or general initializations for this available. Add support for that. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Andy Lutomirski <luto@kernel.org> Acked-by: John Stultz <john.stultz@linaro.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Matt Rickard <matt@softrans.com.au> Cc: Stephen Boyd <sboyd@kernel.org> Cc: Florian Weimer <fweimer@redhat.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: devel@linuxdriverproject.org Cc: virtualization@lists.linux-foundation.org Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Juergen Gross <jgross@suse.com> Link: https://lkml.kernel.org/r/20180917130706.973042587@linutronix.de
* sched/isolation: Eliminate NO_HZ_FULL_ALLPaul E. McKenney2018-02-161-10/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter") broke CONFIG_NO_HZ_FULL_ALL=y kernels. This breakage is due to the code under CONFIG_NO_HZ_FULL_ALL failing to invoke the shiny new housekeeping functions. This means that rcutorture scenario TREE04 now emits RCU CPU stall warnings due to the RCU grace-period kthreads not being awakened at a time of their choosing, or perhaps even not at all: [ 27.731422] rcu_bh kthread starved for 21001 jiffies! g18446744073709551369 c18446744073709551368 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=3 [ 27.731423] rcu_bh I14936 9 2 0x80080000 [ 27.731435] Call Trace: [ 27.731440] __schedule+0x31a/0x6d0 [ 27.731442] schedule+0x31/0x80 [ 27.731446] schedule_timeout+0x15a/0x320 [ 27.731453] ? call_timer_fn+0x130/0x130 [ 27.731457] rcu_gp_kthread+0x66c/0xea0 [ 27.731458] ? rcu_gp_kthread+0x66c/0xea0 Because no one has complained about CONFIG_NO_HZ_FULL_ALL=y being broken, I hypothesize that no one is in fact using it, other than rcutorture. This commit therefore eliminates CONFIG_NO_HZ_FULL_ALL and updates rcutorture's config files to instead use the nohz_full= kernel parameter to put the desired CPUs into nohz_full mode. Fixes: 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter") Reported-by: kernel test robot <xiaolong.ye@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Wanpeng Li <kernellwp@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Jonathan Corbet <corbet@lwn.net>
* sched/isolation: Make CONFIG_NO_HZ_FULL select CONFIG_CPU_ISOLATIONPaul E. McKenney2017-12-181-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | CONFIG_NO_HZ_FULL doesn't make sense without CONFIG_CPU_ISOLATION. In fact enabling the first without the second is a regression as nohz_full= boot parameter gets silently ignored. Besides this unnatural combination hangs RCU gp kthread when running rcutorture for reasons that are not yet fully understood: rcu_preempt kthread starved for 9974 jiffies! g4294967208 +c4294967207 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=0 rcu_preempt I 7464 8 2 0x80000000 Call Trace: __schedule+0x493/0x620 schedule+0x24/0x40 schedule_timeout+0x330/0x3b0 ? preempt_count_sub+0xea/0x140 ? collect_expired_timers+0xb0/0xb0 rcu_gp_kthread+0x6bf/0xef0 This commit therefore makes NO_HZ_FULL select CPU_ISOLATION, which prevents all these bad behaviours. Reported-by: kernel test robot <xiaolong.ye@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Christoph Lameter <cl@linux.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Wanpeng Li <kernellwp@gmail.com> Fixes: 5c4991e24c69 ("sched/isolation: Split out new CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL") Link: http://lkml.kernel.org/r/1513275507-29200-2-git-send-email-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* timekeeping: Remove CONFIG_GENERIC_TIME_VSYSCALL_OLDMiroslav Lichvar2017-11-141-4/+0
| | | | | | | | | | | | | | | | | | | | | As of d4d1fc61eb38f (ia64: Update fsyscall gettime to use modern vsyscall_update)the last user of CONFIG_GENERIC_TIME_VSYSCALL_OLD have been updated, the legacy support for old-style vsyscall implementations can be removed from the timekeeping code. (Thanks again to Tony Luck for helping remove the last user!) [jstultz: Commit message rework] Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com> Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Stephen Boyd <stephen.boyd@linaro.org> Link: https://lkml.kernel.org/r/1510613491-16695-1-git-send-email-john.stultz@linaro.org
* kernel/time/Kconfig: Fix typo in commentRandy Dunlap2017-11-021-1/+1
| | | | | | | | | | | | Fix typo in Kconfig comment text. Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: John Stultz <john.stultz@linaro.org> Cc: Stephen Boyd <sboyd@codeaurora.org> Cc: Jiri Kosina <trivial@kernel.org> Link: https://lkml.kernel.org/r/0e586dd4-2b27-864e-c252-bc72df52fd01@infradead.org
* rcu: Remove nohz_full full-system-idle state machinePaul E. McKenney2017-06-091-50/+0
| | | | | | | | | | | | | | The NO_HZ_FULL_SYSIDLE full-system-idle capability was added in 2013 by commit 0edd1b1784cb ("nohz_full: Add full-system-idle state machine"), but has not been used. This commit therefore removes it. If it turns out to be needed later, this commit can always be reverted. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
* rcu: Drop RCU_USER_QS in favor of NO_HZ_FULLPaul E. McKenney2015-07-061-2/+0
| | | | | | | | | The RCU_USER_QS Kconfig parameter is now just a synonym for NO_HZ_FULL, so this commit eliminates RCU_USER_QS, replacing all uses with NO_HZ_FULL. Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
* clockevents: Remove CONFIG_GENERIC_CLOCKEVENTS_BUILDThomas Gleixner2015-04-011-6/+0
| | | | | | | | | | | | | This option was for simpler migration to the clock events code. Most architectures have been converted and the option has been disfunctional as a standalone option for quite some time. Remove it. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/5021859.jl9OC1medj@vostro.rjw.lan Signed-off-by: Ingo Molnar <mingo@kernel.org>
* clocksource: Move cycle_last validation to core codeThomas Gleixner2014-07-241-0/+5
| | | | | | | | | | | | | | | | | | | | | | The only user of the cycle_last validation is the x86 TSC. In order to provide NMI safe accessor functions for clock monotonic and monotonic_raw we need to do that in the core. We can't do the TSC specific if (now < cycle_last) now = cycle_last; for the other wrapping around clocksources, but TSC has CLOCKSOURCE_MASK(64) which actually does not mask out anything so if now is less than cycle_last the subtraction will give a negative result. So we can check for that in clocksource_delta() and return 0 for that case. Implement and enable it for x86 Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: John Stultz <john.stultz@linaro.org>
* ktime: Kill non-scalar ktime_t implementation for 2038John Stultz2014-07-231-4/+0
| | | | | | | | | | | | | | | | | | | | | | | | | The non-scalar ktime_t implementation is basically a timespec which has to be changed to support dates past 2038 on 32bit systems. This patch removes the non-scalar ktime_t implementation, forcing the scalar s64 nanosecond version on all architectures. This may have additional performance overhead on some 32bit systems when converting between ktime_t and timespec structures, however the majority of 32bit systems (arm and i386) were already using scalar ktime_t, so no performance regressions will be seen on those platforms. On affected platforms, I'm open to finding optimizations, including avoiding converting to timespecs where possible. [ tglx: We can now cleanup the ktime_t.tv64 mess, but thats a different issue and we can throw a coccinelle script at it ] Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: John Stultz <john.stultz@linaro.org>
* nohz: ensure users are aware boot CPU is not NO_HZ_FULLPaul Gortmaker2014-02-141-1/+1
| | | | | | | | | | | | | | | | | | | | | | This bit of information is in the Kconfig help text: "Note the boot CPU will still be kept outside the range to handle the timekeeping duty." However neither the variable NO_HZ_FULL_ALL, or the prompt convey this important detail, so lets add it to the prompt to make it more explicitly obvious to the average user. Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1391711781-7466-1-git-send-email-paul.gortmaker@windriver.com Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
* nohz: Drop generic vtime obsolete dependency on CONFIG_64BITKevin Hilman2013-09-301-1/+0
| | | | | | | | | | | | | | The CONFIG_64BIT requirement on vtime can finally be removed since we now depend on HAVE_VIRT_CPU_ACCOUNTING_GEN which already takes care of the arch ability to handle nsecs based cputime_t safely. Signed-off-by: Kevin Hilman <khilman@linaro.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Arm Linux <linux-arm-kernel@lists.infradead.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
* vtime: Add HAVE_VIRT_CPU_ACCOUNTING_GEN KconfigKevin Hilman2013-09-301-0/+1
| | | | | | | | | | | | | | | | | | | | | | | With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. In order to use that feature, arch code should be audited to ensure there are no races in concurrent read/write of cputime_t. For example, reading/writing 64-bit cputime_t on some 32-bit arches may require multiple accesses for low and high value parts, so proper locking is needed to protect against concurrent accesses. Therefore, add CONFIG_HAVE_VIRT_CPU_ACCOUNTING_GEN which arches can enable after they've been audited for potential races. This option is automatically enabled on 64-bit platforms. Feature requested by Frederic Weisbecker. Signed-off-by: Kevin Hilman <khilman@linaro.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Arm Linux <linux-arm-kernel@lists.infradead.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
* Merge branch 'timers-nohz-for-linus' of ↵Linus Torvalds2013-09-041-1/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timers/nohz changes from Ingo Molnar: "It mostly contains fixes and full dynticks off-case optimizations, by Frederic Weisbecker" * 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) nohz: Include local CPU in full dynticks global kick nohz: Optimize full dynticks's sched hooks with static keys nohz: Optimize full dynticks state checks with static keys nohz: Rename a few state variables vtime: Always debug check snapshot source _before_ updating it vtime: Always scale generic vtime accounting results vtime: Optimize full dynticks accounting off case with static keys vtime: Describe overriden functions in dedicated arch headers m68k: hardirq_count() only need preempt_mask.h hardirq: Split preempt count mask definitions context_tracking: Split low level state headers vtime: Fix racy cputime delta update vtime: Remove a few unneeded generic vtime state checks context_tracking: User/kernel broundary cross trace events context_tracking: Optimize context switch off case with static keys context_tracking: Optimize guest APIs off case with static key context_tracking: Optimize main APIs off case with static key context_tracking: Ground setup for static key use context_tracking: Remove full dynticks' hacky dependency on wide context tracking nohz: Only enable context tracking on full dynticks CPUs ...
| * context_tracking: Remove full dynticks' hacky dependency on wide context ↵Frederic Weisbecker2013-08-131-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | tracking Now that the full dynticks subsystem only enables the context tracking on full dynticks CPUs, lets remove the dependency on CONTEXT_TRACKING_FORCE This dependency was a hack to enable the context tracking widely for the full dynticks susbsystem until the latter becomes able to enable it in a more CPU-finegrained fashion. Now CONTEXT_TRACKING_FORCE only stands for testing on archs that work on support for the context tracking while full dynticks can't be used yet due to unmet dependencies. It simulates a system where all CPUs are full dynticks so that RCU user extended quiescent states and dynticks cputime accounting can be tested on the given arch. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Kevin Hilman <khilman@linaro.org>
* | nohz_full: Add full-system-idle state machinePaul E. McKenney2013-08-311-0/+27
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit adds the state machine that takes the per-CPU idle data as input and produces a full-system-idle indication as output. This state machine is driven out of RCU's quiescent-state-forcing mechanism, which invokes rcu_sysidle_check_cpu() to collect per-CPU idle state and then rcu_sysidle_report() to drive the state machine. The full-system-idle state is sampled using rcu_sys_is_idle(), which also drives the state machine if RCU is idle (and does so by forcing RCU to become non-idle). This function returns true if all but the timekeeping CPU (tick_do_timer_cpu) are idle and have been idle long enough to avoid memory contention on the full_sysidle_state state variable. The rcu_sysidle_force_exit() may be called externally to reset the state machine back into non-idle state. For large systems the state machine is driven out of RCU's force-quiescent-state logic, which provides good scalability at the price of millisecond-scale latencies on the transition to full-system-idle state. This is not so good for battery-powered systems, which are usually small enough that they don't need to care about scalability, but which do care deeply about energy efficiency. Small systems therefore drive the state machine directly out of the idle-entry code. The number of CPUs in a "small" system is defined by a new NO_HZ_FULL_SYSIDLE_SMALL Kconfig parameter, which defaults to 8. Note that this is a build-time definition. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> [ paulmck: Use true and false for boolean constants per Lai Jiangshan. ] Reviewed-by: Josh Triplett <josh@joshtriplett.org> [ paulmck: Simplify logic and provide better comments for memory barriers, based on review comments and questions by Lai Jiangshan. ]
* | nohz_full: Add Kconfig parameter for scalable detection of all-idle statePaul E. McKenney2013-08-191-0/+23
|/ | | | | | | | | | | | | | | | At least one CPU must keep the scheduling-clock tick running for timekeeping purposes whenever there is a non-idle CPU. However, with the new nohz_full adaptive-idle machinery, it is difficult to distinguish between all CPUs really being idle as opposed to all non-idle CPUs being in adaptive-ticks mode. This commit therefore adds a Kconfig parameter as a first step towards enabling a scalable detection of full-system idle state. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> [ paulmck: Update help text per Frederic Weisbecker. ] Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* Merge branch 'timers-urgent-for-linus' of ↵Linus Torvalds2013-05-151-5/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer fixes from Thomas Gleixner: - Cure for not using zalloc in the first place, which leads to random crashes with CPUMASK_OFF_STACK. - Revert a user space visible change which broke udev - Add a missing cpu_online early return introduced by the new full dyntick conversions - Plug a long standing race in the timer wheel cpu hotplug code. Sigh... - Cleanup NOHZ per cpu data on cpu down to prevent stale data on cpu up. * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: time: Revert ALWAYS_USE_PERSISTENT_CLOCK compile time optimizaitons timer: Don't reinitialize the cpu base lock during CPU_UP_PREPARE tick: Don't invoke tick_nohz_stop_sched_tick() if the cpu is offline tick: Cleanup NOHZ per cpu data on cpu down tick: Use zalloc_cpumask_var for allocating offstack cpumasks
| * time: Revert ALWAYS_USE_PERSISTENT_CLOCK compile time optimizaitonsJohn Stultz2013-05-141-5/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Kay Sievers noted that the ALWAYS_USE_PERSISTENT_CLOCK config, which enables some minor compile time optimization to avoid uncessary code in mostly the suspend/resume path could cause problems for userland. In particular, the dependency for RTC_HCTOSYS on !ALWAYS_USE_PERSISTENT_CLOCK, which avoids setting the time twice and simplifies suspend/resume, has the side effect of causing the /sys/class/rtc/rtcN/hctosys flag to always be zero, and this flag is commonly used by udev to setup the /dev/rtc symlink to /dev/rtcN, which can cause pain for older applications. While the udev rules could use some work to be less fragile, breaking userland should strongly be avoided. Additionally the compile time optimizations are fairly minor, and the code being optimized is likely to be reworked in the future, so lets revert this change. Reported-by: Kay Sievers <kay@vrfy.org> Signed-off-by: John Stultz <john.stultz@linaro.org> Cc: stable <stable@vger.kernel.org> #3.9 Cc: Feng Tang <feng.tang@intel.com> Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com> Link: http://lkml.kernel.org/r/1366828376-18124-1-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | rcu: Fix full dynticks' dependency on wide RCU nocb modeFrederic Weisbecker2013-05-041-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 0637e029392386e6996f5d6574aadccee8315efa ("nohz: Select wide RCU nocb for full dynticks") intended to force CONFIG_RCU_NOCB_CPU_ALL=y when full dynticks is enabled. However this option is part of a choice menu and Kconfig's "select" instruction has no effect on such targets. Fix this by using reverse dependencies on the targets we don't want instead. Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Christoph Lameter <cl@linux.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Select VIRT_CPU_ACCOUNTING_GEN from full dynticks configFrederic Weisbecker2013-04-261-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Turn the full dynticks passive dependency on VIRT_CPU_ACCOUNTING_GEN to an active one. The full dynticks Kconfig is currently hidden behind the full dynticks cputime accounting, which is an awkward and counter-intuitive layout: the user first has to select the dynticks cputime accounting in order to make the full dynticks feature to be visible. We definetly want it the other way around. The usual way to perform this kind of active dependency is use "select" on the depended target. Now we can't use the Kconfig "select" instruction when the target is a "choice". So this patch inspires on how the RCU subsystem Kconfig interact with its dependencies on SMP and PREEMPT: we make sure that cputime accounting can't propose another option than VIRT_CPU_ACCOUNTING_GEN when NO_HZ_FULL is selected by using the right "depends on" instruction for each cputime accounting choices. v2: Keep full dynticks cputime accounting available even without full dynticks, as per Paul McKenney's suggestion. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Christoph Lameter <cl@linux.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Remove full dynticks' superfluous dependency on RCU treeFrederic Weisbecker2013-04-241-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Remove the dependency on (TREE_RCU || TREE_PREEMPT_RCU). The full dynticks option already depends on SMP which implies (whatever flavour of) RCU tree config anyway. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Select wide RCU nocb for full dynticksFrederic Weisbecker2013-04-221-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It makes testing and implementation much easier as we know in advance that all CPUs are RCU nocbs. Also this prepares to remove the dynamic check for nohz_full= boot mask to be a subset of rcu_nocbs= Eventually this should also help removing the requirement for the boot CPU to be outside the full dynticks range. Suggested-by: Christoph Lameter <cl@linux.com> Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | Merge branch 'timers/nohz-posix-timers-v2' of ↵Ingo Molnar2013-04-211-0/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/nohz Pull posix cpu timers handling on full dynticks from Frederic Weisbecker. Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | nohz: New APIs to re-evaluate the tick on full dynticks CPUsFrederic Weisbecker2013-04-181-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Provide two new helpers in order to notify the full dynticks CPUs about some internal system changes against which they may reconsider the state of their tick. Some practical examples include: posix cpu timers, perf tick and sched clock tick. For now the notifying handler, implemented through IPIs, is a stub that will be implemented when we get the tick stop/restart infrastructure in. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | | nohz: New option to default all CPUs in full dynticks rangeFrederic Weisbecker2013-04-191-0/+10
|/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Provide a new kernel config that defaults all CPUs to be part of the full dynticks range, except the boot one for timekeeping. This default setting is overriden by the nohz_full= boot option if passed by the user. This is helpful for those who don't need a finegrained range of full dynticks CPU and also for automated testing. Suggested-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Improve a bit the full dynticks Kconfig documentationFrederic Weisbecker2013-04-151-3/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Remove the "single task" statement from CONFIG_NO_HZ_FULL title. The constraint can be invalidated when tasks from other sched classes than SCHED_FAIR are running. Moreover it's possible that hrtick join the party in the future. Also add a line about the dependency on SMP. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Align periodic tick Kconfig with other choices' naming conventionFrederic Weisbecker2013-04-151-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Rename CONFIG_PERIODIC_HZ to CONFIG_HZ_PERIODIC in order to stay consistent with other tick implementation entries: CONFIG_HZ_PERIODIC CONFIG_NO_HZ_IDLE CONFIG_NO_HZ_FULL Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Switch from "extended nohz" to "full nohz" based namingFrederic Weisbecker2013-04-151-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | "Extended nohz" was used as a naming base for the full dynticks API and Kconfig symbols. It reflects the fact the system tries to stop the tick in more places than just idle. But that "extended" name is a bit opaque and vague. Rename it to "full" makes it clearer what the system tries to do under this config: try to shutdown the tick anytime it can. The various constraints that prevent that to happen shouldn't be considered as fundamental properties of this feature but rather technical issues that may be solved in the future. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Fix old dynticks idle Kconfig backward compatibilityFrederic Weisbecker2013-04-151-4/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In order to enforce backward compatibility with older config files, we want the new dynticks-idle Kconfig entry to default its value to the one of the old CONFIG_NO_HZ symbol if present. Namely we want: config NO_HZ # old obsolete dynticks idle symbol bool config NO_HZ_IDLE # new dynticks idle symbol default NO_HZ However Kconfig prevents this to work if the old symbol is not visible. And this is currently the case because NO_HZ lacks a title in order to show it in make oldconfig and alike. To fix this, bring a minimal title and help text to the obsolete Kconfig entry that explains its purpose. This makes the "defaulting" to work. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Pack nohz Kconfig option in a menu of choicesFrederic Weisbecker2013-04-031-5/+23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now the user has the choice between three implementations of the timer tick: * Static periodic tick * Idle dynticks * Full dynticks At least for now, these are mutually exclusive choices, so let's rely on the proper Kconfig feature to display these to the user. A new entry CONFIG_NO_HZ_IDLE is created and the old CONFIG_NO_HZ maps to it for config file backward compatibility. The old name was too general now that we have more granular dynticks implementations. While at it, add some explanation to help the user on his decision between the 3 entries. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Rename CONFIG_NO_HZ to CONFIG_NO_HZ_COMMONFrederic Weisbecker2013-04-031-4/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We are planning to convert the dynticks Kconfig options layout into a choice menu. The user must be able to easily pick any of the following implementations: constant periodic tick, idle dynticks, full dynticks. As this implies a mutual exclusion, the two dynticks implementions need to converge on the selection of a common Kconfig option in order to ease the sharing of a common infrastructure. It would thus seem pretty natural to reuse CONFIG_NO_HZ to that end. It already implements all the idle dynticks code and the full dynticks depends on all that code for now. So ideally the choice menu would propose CONFIG_NO_HZ_IDLE and CONFIG_NO_HZ_EXTENDED then both would select CONFIG_NO_HZ. On the other hand we want to stay backward compatible: if CONFIG_NO_HZ is set in an older config file, we want to enable CONFIG_NO_HZ_IDLE by default. But we can't afford both at the same time or we run into a circular dependency: 1) CONFIG_NO_HZ_IDLE and CONFIG_NO_HZ_EXTENDED both select CONFIG_NO_HZ 2) If CONFIG_NO_HZ is set, we default to CONFIG_NO_HZ_IDLE We might be able to support that from Kconfig/Kbuild but it may not be wise to introduce such a confusing behaviour. So to solve this, create a new CONFIG_NO_HZ_COMMON option which gathers the common code between idle and full dynticks (that common code for now is simply the idle dynticks code) and select it from their referring Kconfig. Then we'll later create CONFIG_NO_HZ_IDLE and map CONFIG_NO_HZ to it for backward compatibility. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Unhide full dynticks feature from its dependenciesFrederic Weisbecker2013-04-021-5/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The full dynticks feature only shows up when all its Kconfig dependencies are met (RCU nocbs, RCU user mode, ...) This is far from being user friendly as those who want to activate this feature need to look into the Kconfig files and iterate through each dependency then activate these by hand in order to show and select the full dynticks Kconfig option. So process the other way around: show up the Kconfig option if the minimal low level dependencies are met and activate the high level ones when we enable the feature. Note there is one exception in the picture: CONFIG_VIRT_CPU_ACCOUNTING_GEN is part of a Kconfig choice menu and it appears we can't select it from another Kconfig selection when it's under such layout. So for now this particular item stays as a passive dependency. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* | nohz: Basic full dynticks interfaceFrederic Weisbecker2013-03-211-0/+19
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For extreme usecases such as Real Time or HPC, having the ability to shutdown the tick when a single task runs on a CPU is a desired feature: * Reducing the amount of interrupts improves throughput for CPU-bound tasks. The CPU is less distracted from its real job, from an execution time and from the cache point of views. * This also improve latency response as we have less critical sections. Start with introducing a very simple interface to define full dynticks CPU: use a boot time option defined cpumask through the "nohz_extended=" kernel parameter. CPUs that are part of this range will have their tick shutdown whenever possible: provided they run a single task and they don't do kernel activity that require the periodic tick. These details will be later documented in Documentation/* An online CPU must be kept outside this range to handle the timekeeping. Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
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