The circular buffers are now validated with selftests. The next interrupt
index algorithm which is the hardest part to validate needs extra coverage.
Add a selftest which uses the intervals stored in the arrays and insert all
the values except the last one. The next event computation must return the
same value as the last element which was not inserted.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20190527205521.12091-9-daniel.lezcano@linaro.org
Due to the complexity of the code and the difficulty to debug it, add some
selftests to the framework in order to spot issues or regression at boot
time when the runtime testing is enabled for this subsystem.
This tests the circular buffer at the limits and validates:
- the encoding / decoding of the values
- the macro to browse the irq timings circular buffer
- the function to push data in the circular buffer
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20190527205521.12091-7-daniel.lezcano@linaro.org
For the next patches providing the selftest, it is required to insert
interval values directly in the buffer in order to check the correctness of
the code. Encapsulate the code doing that in a always inline function in
order to reuse it in the test code.
No functional changes.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20190527205521.12091-6-daniel.lezcano@linaro.org
With a minimal period and if there is a period which is a multiple of it
but lesser than the max period then it will be detected before and the
minimal period will be never reached.
1 2 1 2 1 2 1 2 1 2 1 2
<-----> <-----> <----->
<-> <-> <-> <-> <-> <->
In that case, the minimum period is 2 and the maximum period is 5. That
means all repeating pattern of 2 will be detected as repeating pattern of
4, it is pointless to go up to 2 when searching for the period as it will
always fail.
Remove one loop iteration by increasing the minimal period to 3.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20190527205521.12091-4-daniel.lezcano@linaro.org
It appears the index beginning computation is not correct, the current
code does:
i = (irqts->count & IRQ_TIMINGS_MASK) - 1
If irqts->count is equal to zero, we end up with an index equal to -1,
but that does not happen because the function checks against zero
before and returns in such case.
However, if irqts->count is a multiple of IRQ_TIMINGS_SIZE, the
resulting & bit op will be zero and leads also to a -1 index.
Re-introduce the iteration loop belonging to the previous variance
code which was correct.
Fixes: bbba0e7c5c "genirq/timings: Add array suffix computation code"
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20190527205521.12091-3-daniel.lezcano@linaro.org
The current code is luckily working with most of the interval samples
testing but actually it fails to correctly detect pattern repetition
breaking at the end of the buffer.
Narrowing down the bug has been a real pain because of the pointers,
so the routine is rewrittne by using indexes instead.
Fixes: bbba0e7c5c "genirq/timings: Add array suffix computation code"
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20190527205521.12091-2-daniel.lezcano@linaro.org
The previous approach based on the variance was discarding values from
the timings when they were considered as anomalies as stated by the
normal law statistical model.
However in the interrupt life, there can be multiple anomalies due to the
nature of the device generating the interrupts, and most of the time a
repeating pattern can be observed, that is particulary true for network,
console, MMC or SSD devices.
The variance approach missed the patterns and it was only able to deal with
the interrupt coming in regular intervals, thus reducing considerably the
scope of what is predictable.
In order to find out the repeating patterns, the interrupt intervals are
grouped in a ilog2 basis to create a suite of numbers with small
amplitude. Every group contains an exponential moving average of the values
belonging to the group. The array suffix, a data structure used for string
searching, data compression, etc ..., is built from the suite of numbers
and the suffixes are then searched in this suite.
The tests showed the algorithm is able to find all repeating patterns,
as well as regular interval in less than 1us on x86-i7.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: rjw@rjwysocki.net
Cc: ulf.hansson@linaro.org
Cc: linux-pm@vger.kernel.org
Link: https://lkml.kernel.org/r/20190328151336.5316-2-daniel.lezcano@linaro.org
The variance computation did not provide the expected results and will be
replaced with a different approach to compute the next interrupt based on
the array suffixes derived algorithm.
There is no good way to transform the variance code to the new algorithm,
so for ease of review remove the existing code first.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: rjw@rjwysocki.net
Cc: ulf.hansson@linaro.org
Cc: linux-pm@vger.kernel.org
Link: https://lkml.kernel.org/r/20190328151336.5316-1-daniel.lezcano@linaro.org
Now that SPDX identifiers are in place, remove the boilerplate or
references.
The change in timings.c has been acked by the author.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Link: https://lkml.kernel.org/r/20180314212030.668321222@linutronix.de
Add SPDX identifiers to files
- which contain an explicit license boiler plate or reference
- which do not contain a license reference and were not updated in the
initial SPDX conversion because the license was deduced by the scanners
via EXPORT_SYMBOL_GPL as GPL2.0 only.
[ tglx: Moved adding identifiers from the patch which removes the
references/boilerplate ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Link: https://lkml.kernel.org/r/20180314212030.668321222@linutronix.de
Remove pointless references to the file name itself and condense the
information so it wastes less space.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Link: https://lkml.kernel.org/r/20180314212030.412095827@linutronix.de
Use lockdep to check that IRQs are enabled or disabled as expected. This
way the sanity check only shows overhead when concurrency correctness
debug code is enabled.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David S . Miller <davem@davemloft.net>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1509980490-4285-10-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
An interrupt behaves with a burst of activity with periodic interval of time
followed by one or two peaks of longer interval.
As the time intervals are periodic, statistically speaking they follow a normal
distribution and each interrupts can be tracked individually.
Add a mechanism to compute the statistics on all interrupts, except the
timers which are deterministic from a prediction point of view, as their
expiry time is known.
The goal is to extract the periodicity for each interrupt, with the last
timestamp and sum them, so the next event can be predicted to a certain
extent.
Taking the earliest prediction gives the expected wakeup on the system
(assuming a timer won't expire before).
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: "Rafael J . Wysocki" <rafael@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: http://lkml.kernel.org/r/1498227072-5980-2-git-send-email-daniel.lezcano@linaro.org
The interrupt framework gives a lot of information about each interrupt. It
does not keep track of when those interrupts occur though, which is a
prerequisite for estimating the next interrupt arrival for power management
purposes.
Add a mechanism to record the timestamp for each interrupt occurrences in a
per-CPU circular buffer to help with the prediction of the next occurrence
using a statistical model.
Each CPU can store up to IRQ_TIMINGS_SIZE events <irq, timestamp>, the
current value of IRQ_TIMINGS_SIZE is 32.
Each event is encoded into a single u64, where the high 48 bits are used
for the timestamp and the low 16 bits are for the irq number.
A static key is introduced so when the irq prediction is switched off at
runtime, the overhead is near to zero.
It results in most of the code in internals.h for inline reasons and a very
few in the new file timings.c. The latter will contain more in the next patch
which will provide the statistical model for the next event prediction.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: "Rafael J . Wysocki" <rafael@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: http://lkml.kernel.org/r/1498227072-5980-1-git-send-email-daniel.lezcano@linaro.org
