linux.git/include/linux/context_tracking.h, branch v4.1.29

kvm,rcu,nohz: use RCU extended quiescent state when running KVM guest

2015-03-09T14:43:03+00:00

The host kernel is not doing anything while the CPU is executing
a KVM guest VCPU, so it can be marked as being in an extended
quiescent state, identical to that used when running user space
code.

The only exception to that rule is when the host handles an
interrupt, which is already handled by the irq code, which
calls rcu_irq_enter and rcu_irq_exit.

The guest_enter and guest_exit functions already switch vtime
accounting independent of context tracking. Leave those calls
where they are, instead of moving them into the context tracking
code.

Reviewed-by: Paul E. McKenney 
Signed-off-by: Rik van Riel 
Cc: Paul E. McKenney 
Cc: Andy Lutomirski 
Cc: Will deacon 
Cc: Marcelo Tosatti 
Cc: Christian Borntraeger 
Cc: Luiz Capitulino 
Cc: Paolo Bonzini 
Signed-off-by: Frederic Weisbecker

context_tracking: Generalize context tracking APIs to support user and guest

2015-03-09T14:42:52+00:00

Generalize the context tracking APIs to support various nature of
contexts. This is performed by splitting out the mechanism from
context_tracking_user_enter and context_tracking_user_exit into
context_tracking_enter and context_tracking_exit.

The nature of the context we track is now detailed in a ctx_state
parameter pushed to these APIs, allowing the same functions to not just
track kernel <> user space switching, but also kernel <> guest transitions.

But leave the old functions in order to avoid breaking ARM, which calls
these functions from assembler code, and cannot easily use C enum
parameters.

Reviewed-by: Paul E. McKenney 
Signed-off-by: Rik van Riel 
Cc: Paul E. McKenney 
Cc: Andy Lutomirski 
Cc: Will deacon 
Cc: Marcelo Tosatti 
Cc: Christian Borntraeger 
Cc: Luiz Capitulino 
Cc: Paolo Bonzini 
Signed-off-by: Frederic Weisbecker

context_tracking: Rename context symbols to prepare for transition state

2015-03-09T14:42:50+00:00

Current context tracking symbols are designed to express living state.
As such they are prefixed with "IN_": IN_USER, IN_KERNEL.

Now we are going to use these symbols to also express state transitions
such as context_tracking_enter(IN_USER) or context_tracking_exit(IN_USER).
But while the "IN_" prefix works well to express entering a context, it's
confusing to depict a context exit: context_tracking_exit(IN_USER)
could mean two things:
	1) We are exiting the current context to enter user context.
	2) We are exiting the user context
We want 2) but the reviewer may be confused and understand 1)

So lets disambiguate these symbols and rename them to CONTEXT_USER and
CONTEXT_KERNEL.

Acked-by: Rik van Riel 
Cc: Paul E. McKenney 
Cc: Andy Lutomirski 
Cc: Will deacon 
Cc: Marcelo Tosatti 
Cc: Christian Borntraeger 
Cc: Luiz Capitulino 
Cc: Paolo Bonzini 
Signed-off-by: Frederic Weisbecker

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

context_tracking: Split low level state headers

2013-08-14T15:14:51+00:00

We plan to use the context tracking static key on inline
vtime APIs. For this we need to include the context tracking
headers from those of vtime.

However vtime headers need to stay low level because they are
included in hardirq.h that mostly contains standalone
definitions. But context_tracking.h includes sched.h for
a few task_struct references, therefore it wouldn't be sensible
to include it from vtime.h

To solve this, lets split the context tracking headers and move
out the pure state definitions that only require a few low level
headers. We can safely include that small part in vtime.h later.

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

context_tracking: Optimize context switch off case with static keys

2013-08-14T15:14:47+00:00

No need for syscall slowpath if no CPU is full dynticks,
rather nop this in this case.

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

context_tracking: Optimize guest APIs off case with static key

2013-08-14T15:14:46+00:00

Optimize guest entry/exit APIs with static keys. This minimize
the overhead for those who enable CONFIG_NO_HZ_FULL without
always using it. Having no range passed to nohz_full= should
result in the probes overhead to be minimized.

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

context_tracking: Optimize main APIs off case with static key

2013-08-14T15:14:45+00:00

Optimize user and exception entry/exit APIs with static
keys. This minimize the overhead for those who enable
CONFIG_NO_HZ_FULL without always using it. Having no range
passed to nohz_full= should result in the probes to be nopped
(at least we hope so...).

If this proves not be enough in the long term, we'll need
to bring an exception slow path by re-routing the exception
handlers.

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

context_tracking: Ground setup for static key use

2013-08-14T15:12:46+00:00

Prepare for using a static key in the context tracking subsystem.
This will help optimizing the off case on its many users:

* user_enter, user_exit, exception_enter, exception_exit, guest_enter,
  guest_exit, vtime_*()

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