user/sven/linux.git/kernel/time/timer_list.c, branch v4.2-rc4

timer: Reduce timer migration overhead if disabled

2015-06-19T13:18:28Z

Eric reported that the timer_migration sysctl is not really nice performance wise as it needs to check at every timer insertion whether the feature is enabled or not. Further the check does not live in the timer code, so we have an extra function call which checks an extra cache line to figure out that it is disabled. We can do better and store that information in the per cpu (hr)timer bases. I pondered to use a static key, but that's a nightmare to update from the nohz code and the timer base cache line is hot anyway when we select a timer base. The old logic enabled the timer migration unconditionally if CONFIG_NO_HZ was set even if nohz was disabled on the kernel command line. With this modification, we start off with migration disabled. The user visible sysctl is still set to enabled. If the kernel switches to NOHZ migration is enabled, if the user did not disable it via the sysctl prior to the switch. If nohz=off is on the kernel command line, migration stays disabled no matter what. Before: 47.76% hog [.] main 14.84% [kernel] [k] _raw_spin_lock_irqsave 9.55% [kernel] [k] _raw_spin_unlock_irqrestore 6.71% [kernel] [k] mod_timer 6.24% [kernel] [k] lock_timer_base.isra.38 3.76% [kernel] [k] detach_if_pending 3.71% [kernel] [k] del_timer 2.50% [kernel] [k] internal_add_timer 1.51% [kernel] [k] get_nohz_timer_target 1.28% [kernel] [k] __internal_add_timer 0.78% [kernel] [k] timerfn 0.48% [kernel] [k] wake_up_nohz_cpu After: 48.10% hog [.] main 15.25% [kernel] [k] _raw_spin_lock_irqsave 9.76% [kernel] [k] _raw_spin_unlock_irqrestore 6.50% [kernel] [k] mod_timer 6.44% [kernel] [k] lock_timer_base.isra.38 3.87% [kernel] [k] detach_if_pending 3.80% [kernel] [k] del_timer 2.67% [kernel] [k] internal_add_timer 1.33% [kernel] [k] __internal_add_timer 0.73% [kernel] [k] timerfn 0.54% [kernel] [k] wake_up_nohz_cpu Reported-by: Eric Dumazet Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Paul McKenney Cc: Frederic Weisbecker Cc: Viresh Kumar Cc: John Stultz Cc: Joonwoo Park Cc: Wenbo Wang Link: http://lkml.kernel.org/r/20150526224512.127050787@linutronix.de Signed-off-by: Thomas Gleixner

clockevents: Introduce CLOCK_EVT_STATE_ONESHOT_STOPPED state

2015-05-19T14:18:02Z

When no timers/hrtimers are pending, the expiry time is set to a special value: 'KTIME_MAX'. This normally happens with NO_HZ_{IDLE|FULL} in both LOWRES/HIGHRES modes. When 'expiry == KTIME_MAX', we either cancel the 'tick-sched' hrtimer (NOHZ_MODE_HIGHRES) or skip reprogramming clockevent device (NOHZ_MODE_LOWRES). But, the clockevent device is already reprogrammed from the tick-handler for next tick. As the clock event device is programmed in ONESHOT mode it will at least fire one more time (unnecessarily). Timers on few implementations (like arm_arch_timer, etc.) only support PERIODIC mode and their drivers emulate ONESHOT over that. Which means that on these platforms we will get spurious interrupts periodically (at last programmed interval rate, normally tick rate). In order to avoid spurious interrupts, the clockevent device should be stopped or its interrupts should be masked. A simple (yet hacky) solution to get this fixed could be: update hrtimer_force_reprogram() to always reprogram clockevent device and update clockevent drivers to STOP generating events (or delay it to max time) when 'expires' is set to KTIME_MAX. But the drawback here is that every clockevent driver has to be hacked for this particular case and its very easy for new ones to miss this. However, Thomas suggested to add an optional state ONESHOT_STOPPED to solve this problem: lkml.org/lkml/2014/5/9/508. This patch adds support for ONESHOT_STOPPED state in clockevents core. It will only be available to drivers that implement the state-specific callbacks instead of the legacy ->set_mode() callback. Signed-off-by: Viresh Kumar Reviewed-by: Preeti U. Murthy Cc: linaro-kernel@lists.linaro.org Cc: Frederic Weisbecker Cc: Kevin Hilman Cc: Daniel Lezcano Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/b8b383a03ac07b13312c16850b5106b82e4245b5.1428031396.git.viresh.kumar@linaro.org Signed-off-by: Thomas Gleixner

tick-broadcast: Fix the printing of broadcast masks

2015-05-05T08:35:58Z

Today the number of bits of the broadcast masks that is output into /proc/timer_list is sizeof(unsigned long). This means that on machines with a larger number of CPUs, the bitmasks of CPUs beyond this range do not appear. Fix this by using bitmap printing through "%*pb" instead, so as to output the broadcast masks for the range of nr_cpu_ids into /proc/timer_list. Signed-off-by: Preeti U Murthy Cc: peterz@infradead.org Cc: linuxppc-dev@ozlabs.org Cc: john.stultz@linaro.org Link: http://lkml.kernel.org/r/20150428084520.3314.62668.stgit@preeti.in.ibm.com Signed-off-by: Thomas Gleixner

tick: Nohz: Rework next timer evaluation

2015-04-22T15:06:50Z

The evaluation of the next timer in the nohz code is based on jiffies while all the tick internals are nano seconds based. We have also to convert hrtimer nanoseconds to jiffies in the !highres case. That's just wrong and introduces interesting corner cases. Turn it around and convert the next timer wheel timer expiry and the rcu event to clock monotonic and base all calculations on nanoseconds. That identifies the case where no timer is pending clearly with an absolute expiry value of KTIME_MAX. Makes the code more readable and gets rid of the jiffies magic in the nohz code. Signed-off-by: Thomas Gleixner Reviewed-by: Paul E. McKenney Acked-by: Peter Zijlstra Cc: Preeti U Murthy Cc: Viresh Kumar Cc: Marcelo Tosatti Cc: Frederic Weisbecker Cc: Josh Triplett Cc: Lai Jiangshan Cc: John Stultz Cc: Marcelo Tosatti Link: http://lkml.kernel.org/r/20150414203502.184198593@linutronix.de Signed-off-by: Thomas Gleixner

hrtimer: Make the statistics fields smaller

2015-04-22T15:06:49Z

No point in having usigned long for /proc/timer_list statistics. Make them unsigned int. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Cc: Preeti U Murthy Cc: Viresh Kumar Cc: Marcelo Tosatti Cc: Frederic Weisbecker Link: http://lkml.kernel.org/r/20150414203500.959773467@linutronix.de Signed-off-by: Thomas Gleixner

hrtimer: Get rid of the resolution field in hrtimer_clock_base

2015-04-22T15:06:48Z

The field has no value because all clock bases have the same resolution. The resolution only changes when we switch to high resolution timer mode. We can evaluate that from a single static variable as well. In the !HIGHRES case its simply a constant. Export the variable, so we can simplify the usage sites. Signed-off-by: Thomas Gleixner Reviewed-by: Preeti U Murthy Acked-by: Peter Zijlstra Cc: Viresh Kumar Cc: Marcelo Tosatti Cc: Frederic Weisbecker Link: http://lkml.kernel.org/r/20150414203500.645454122@linutronix.de Signed-off-by: Thomas Gleixner

timer_list: Reduce SEQ_printf footprint

2015-04-22T10:03:39Z

This macro can be converted to a static function to reduce object size. (x86-64 defconfig) $ size kernel/time/timer_list.o* text data bss dec hex filename 6583 8 0 6591 19bf kernel/time/timer_list.o.old 4647 8 0 4655 122f kernel/time/timer_list.o.new Signed-off-by: Joe Perches Cc: John Stultz Link: http://lkml.kernel.org/r/1429295958.2850.104.camel@perches.com Signed-off-by: Thomas Gleixner

tick: Move core only declarations and functions to core

2015-04-01T12:22:58Z

No point to expose everything to the world. People just believe such functions can be abused for whatever purposes. Sigh. Signed-off-by: Thomas Gleixner [ Rebased on top of 4.0-rc5 ] Signed-off-by: Rafael J. Wysocki Cc: Nicolas Pitre Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/28017337.VbCUc39Gme@vostro.rjw.lan [ Merged to latest timers/core ] Signed-off-by: Ingo Molnar

clockevents: Manage device's state separately for the core

2015-03-27T09:26:19Z

'enum clock_event_mode' is used for two purposes today: - to pass mode to the driver of clockevent device::set_mode(). - for managing state of the device for clockevents core. For supporting new modes/states we have moved away from the legacy set_mode() callback to new per-mode/state callbacks. New modes/states shouldn't be exposed to the legacy (now OBSOLOTE) callbacks and so we shouldn't add new states to 'enum clock_event_mode'. Lets have separate enums for the two use cases mentioned above. Keep using the earlier enum for legacy set_mode() callback and mark it OBSOLETE. And add another enum to clearly specify the possible states of a clockevent device. This also renames the newly added per-mode callbacks to reflect state changes. We haven't got rid of 'mode' member of 'struct clock_event_device' as it is used by some of the clockevent drivers and it would automatically die down once we migrate those drivers to the new interface. It ('mode') is only updated now for the drivers using the legacy interface. Suggested-by: Peter Zijlstra Suggested-by: Ingo Molnar Signed-off-by: Viresh Kumar Acked-by: Peter Zijlstra Cc: Daniel Lezcano Cc: Frederic Weisbecker Cc: Kevin Hilman Cc: Preeti U Murthy Cc: linaro-kernel@lists.linaro.org Cc: linaro-networking@linaro.org Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/b6b0143a8a57bd58352ad35e08c25424c879c0cb.1425037853.git.viresh.kumar@linaro.org Signed-off-by: Ingo Molnar

clockevents: Handle tick device's resume separately

2015-03-27T09:26:19Z

Upcoming patch will redefine possible states of a clockevent device. The RESUME mode is a special case only for tick's clockevent devices. In future it can be replaced by ->resume() callback already available for clockevent devices. Lets handle it separately so that clockevents_set_mode() only handles states valid across all devices. This also renames set_mode_resume() to tick_resume() to make it more explicit. Signed-off-by: Viresh Kumar Acked-by: Peter Zijlstra Cc: Daniel Lezcano Cc: Frederic Weisbecker Cc: Kevin Hilman Cc: Peter Zijlstra Cc: Preeti U Murthy Cc: linaro-kernel@lists.linaro.org Cc: linaro-networking@linaro.org Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/c1b0112410870f49e7bf06958e1483eac6c15e20.1425037853.git.viresh.kumar@linaro.org Signed-off-by: Ingo Molnar