linux-toradex.git/include/linux/vtime.h, branch v4.8-rc1

sched/cputime: Reorganize vtime native irqtime accounting headers

2016-07-14T08:42:35+00:00

The vtime irqtime accounting headers are very scattered and convoluted
right now. Reorganize them such that it is obvious that only
CONFIG_VIRT_CPU_ACCOUNTING_NATIVE does use it.

Signed-off-by: Frederic Weisbecker 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Paolo Bonzini 
Cc: Peter Zijlstra 
Cc: Radim Krcmar 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: Wanpeng Li 
Link: http://lkml.kernel.org/r/1468421405-20056-5-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

sched/cputime: Clean up the old vtime gen irqtime accounting completely

2016-07-14T08:42:35+00:00

Vtime generic irqtime accounting has been removed but there are a few
remnants to clean up:

* The vtime_accounting_cpu_enabled() check in irq entry was only used
  by CONFIG_VIRT_CPU_ACCOUNTING_GEN. We can safely remove it.

* Without the vtime_accounting_cpu_enabled(), we no longer need to
  have a vtime_common_account_irq_enter() indirect function.

* Move vtime_account_irq_enter() implementation under
  CONFIG_VIRT_CPU_ACCOUNTING_NATIVE which is the last user.

* The vtime_account_user() call was only used on irq entry for
  CONFIG_VIRT_CPU_ACCOUNTING_GEN. We can remove that too.

Signed-off-by: Frederic Weisbecker 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Paolo Bonzini 
Cc: Peter Zijlstra 
Cc: Radim Krcmar 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: Wanpeng Li 
Link: http://lkml.kernel.org/r/1468421405-20056-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

sched/cputime: Replace VTIME_GEN irq time code with IRQ_TIME_ACCOUNTING code

2016-07-14T08:42:34+00:00

The CONFIG_VIRT_CPU_ACCOUNTING_GEN irq time tracking code does not
appear to currently work right.

On CPUs without nohz_full=, only tick based irq time sampling is
done, which breaks down when dealing with a nohz_idle CPU.

On firewalls and similar systems, no ticks may happen on a CPU for a
while, and the irq time spent may never get accounted properly. This
can cause issues with capacity planning and power saving, which use
the CPU statistics as inputs in decision making.

Remove the VTIME_GEN vtime irq time code, and replace it with the
IRQ_TIME_ACCOUNTING code, when selected as a config option by the user.

Signed-off-by: Rik van Riel 
Signed-off-by: Frederic Weisbecker 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Paolo Bonzini 
Cc: Peter Zijlstra 
Cc: Radim Krcmar 
Cc: Thomas Gleixner 
Cc: Wanpeng Li 
Link: http://lkml.kernel.org/r/1468421405-20056-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

sched/cputime: Introduce vtime accounting check for readers

2015-12-04T09:34:45+00:00

Readers need to know if vtime runs at all on some CPU somewhere, this
is a fast-path check to determine if we need to check further the need
to add up any tickless cputime delta.

This fast path check uses context tracking state because vtime is tied
to context tracking as of now. This check appears to be confusing though
so lets use a vtime function that deals with context tracking details
in vtime implementation instead.

Signed-off-by: Frederic Weisbecker 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Chris Metcalf 
Cc: Christoph Lameter 
Cc: Hiroshi Shimamoto 
Cc: Linus Torvalds 
Cc: Luiz Capitulino 
Cc: Mike Galbraith 
Cc: Paul E . McKenney 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1447948054-28668-7-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

sched/cputime: Rename vtime_accounting_enabled() to vtime_accounting_cpu_enabled()

2015-12-04T09:34:45+00:00

vtime_accounting_enabled() checks if vtime is running on the current CPU
and is as such a misnomer. Lets rename it to a function that reflect its
locality. We are going to need the current name for a function that tells
if vtime runs at all on some CPU.

Signed-off-by: Frederic Weisbecker 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Chris Metcalf 
Cc: Christoph Lameter 
Cc: Hiroshi Shimamoto 
Cc: Linus Torvalds 
Cc: Luiz Capitulino 
Cc: Mike Galbraith 
Cc: Paul E . McKenney 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1447948054-28668-6-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

context_tracking: Rename context_tracking_active() to context_tracking_cpu_is_enabled()

2013-12-02T19:43:15+00:00

We currently have a confusing couple of API naming with the existing
context_tracking_active() and context_tracking_is_enabled().

Lets keep the latter one, context_tracking_is_enabled(), for global
context tracking state check and use context_tracking_cpu_is_enabled()
for local state check.

Signed-off-by: Frederic Weisbecker 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Oleg Nesterov 
Cc: Steven Rostedt

context_tracking: Wrap static key check into more intuitive function name

2013-12-02T19:43:14+00:00

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

vtime: Optimize full dynticks accounting off case with static keys

2013-08-14T15:14:54+00:00

If no CPU is in the full dynticks range, we can avoid the full
dynticks cputime accounting through generic vtime along with its
overhead and use the traditional tick based accounting instead.

Let's do this and nope the off case 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

vtime: Describe overriden functions in dedicated arch headers

2013-08-14T15:14:53+00:00

If the arch overrides some generic vtime APIs, let it describe
these on a dedicated and standalone header. This way it becomes
convenient to include it in vtime generic headers without irrelevant
stuff in such a low level header.

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 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens

vtime: Use consistent clocks among nohz accounting

2013-05-31T09:31:50+00:00

While computing the cputime delta of dynticks CPUs,
we are mixing up clocks of differents natures:

* local_clock() which takes care of unstable clock
sources and fix these if needed.

* sched_clock() which is the weaker version of
local_clock(). It doesn't compute any fixup in case
of unstable source.

If the clock source is stable, those two clocks are the
same and we can safely compute the difference against
two random points.

Otherwise it results in random deltas as sched_clock()
can randomly drift away, back or forward, from local_clock().

As a consequence, some strange behaviour with unstable tsc
has been observed such as non progressing constant zero cputime.
(The 'top' command showing no load).

Fix this by only using local_clock(), or its irq safe/remote
equivalent, in vtime code.

Reported-by: Mike Galbraith 
Suggested-by: Mike Galbraith 
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 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Ingo Molnar