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  1. 03 4月, 2013 1 次提交
    • F
      nohz: Unhide full dynticks feature from its dependencies · ab71d36d
      由 Frederic Weisbecker 提交于 
      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: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NFrederic 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>
      ab71d36d
  3. 21 3月, 2013 3 次提交
    • F
      nohz: Wake up full dynticks CPUs when a timer gets enqueued · 1c20091e
      由 Frederic Weisbecker 提交于 
      Wake up a CPU when a timer list timer is enqueued there and
the target is part of the full dynticks range. Sending an IPI
to it makes it reconsidering the next timer to program on top
of recent updates.

This may later be improved by checking if the tick is really
stopped on the target. This would need some careful
synchronization though. So deal with such optimization later
and start simple.
Signed-off-by: NFrederic 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>
      1c20091e
    • F
      nohz: Assign timekeeping duty to a CPU outside the full dynticks range · a382bf93
      由 Frederic Weisbecker 提交于 
      This way the full nohz CPUs can safely run with the tick
stopped with a guarantee that somebody else is taking
care of the jiffies and GTOD progression.

Once the duty is attributed to a CPU, it won't change. Also that
CPU can't enter into dyntick idle mode or be hot unplugged.

This may later be improved from a power consumption POV. At
least we should be able to share the duty amongst all CPUs
outside the full dynticks range. Then the duty could even be
shared with full dynticks CPUs when those can't stop their
tick for any reason.

But let's start with that very simple approach first.
Signed-off-by: NFrederic 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>
[fix have_nohz_full_mask offcase]
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      a382bf93
    • F
      nohz: Basic full dynticks interface · a831881b
      由 Frederic Weisbecker 提交于 
      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: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NFrederic 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>
      a831881b
  5. 18 3月, 2013 1 次提交
  7. 14 3月, 2013 2 次提交
    • A
      sched: Fix variable name misnomer, add comments · 1bf08230
      由 Andrei Epure 提交于 
      The min_vruntime variable actually stores the maximum value.
The added comment was taken from place_entity function.
Signed-off-by: NAndrei Epure <epure.andrei@gmail.com>
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1363115544-1964-1-git-send-email-epure.andrei@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      1bf08230
    • F
      sched: Lower chances of cputime scaling overflow · d9a3c982
      由 Frederic Weisbecker 提交于 
      Some users have reported that after running a process with
hundreds of threads on intensive CPU-bound loads, the cputime
of the group started to freeze after a few days.

This is due to how we scale the tick-based cputime against
the scheduler precise execution time value.

We add the values of all threads in the group and we multiply
that against the sum of the scheduler exec runtime of the whole
group.

This easily overflows after a few days/weeks of execution.

A proposed solution to solve this was to compute that multiplication
on stime instead of utime:
   62188451
   ("cputime: Avoid multiplication overflow on utime scaling")

The rationale behind that was that it's easy for a thread to
spend most of its time in userspace under intensive CPU-bound workload
but it's much harder to do CPU-bound intensive long run in the kernel.

This postulate got defeated when a user recently reported he was still
seeing cputime freezes after the above patch. The workload that
triggers this issue relates to intensive networking workloads where
most of the cputime is consumed in the kernel.

To reduce much more the opportunities for multiplication overflow,
lets reduce the multiplication factors to the remainders of the division
between sched exec runtime and cputime. Assuming the difference between
these shouldn't ever be that large, it could work on many situations.

This gets the same results as in the upstream scaling code except for
a small difference: the upstream code always rounds the results to
the nearest integer not greater to what would be the precise result.
The new code rounds to the nearest integer either greater or not
greater. In practice this difference probably shouldn't matter but
it's worth mentioning.

If this solution appears not to be enough in the end, we'll
need to partly revert back to the behaviour prior to commit
     0cf55e1e
     ("sched, cputime: Introduce thread_group_times()")

Back then, the scaling was done on exit() time before adding the cputime
of an exiting thread to the signal struct. And then we'll need to
scale one-by-one the live threads cputime in thread_group_cputime(). The
drawback may be a slightly slower code on exit time.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
      d9a3c982
  9. 11 3月, 2013 2 次提交
  11. 08 3月, 2013 2 次提交
    • F
      cputime: Dynamically scale cputime for full dynticks accounting · 9fbc42ea
      由 Frederic Weisbecker 提交于 
      The full dynticks cputime accounting is able to account either
using the tick or the context tracking subsystem. This way
the housekeeping CPU can keep the low overhead tick based
solution.

This latter mode has a low jiffies resolution granularity and
need to be scaled against CFS precise runtime accounting to
improve its result. We are doing this for CONFIG_TICK_CPU_ACCOUNTING,
now we also need to expand it to full dynticks accounting dynamic
off-case as well.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Mats Liljegren <mats.liljegren@enea.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      9fbc42ea
    • F
      context_tracking: Restore preempted context state after preempt_schedule_irq() · b22366cd
      由 Frederic Weisbecker 提交于 
      From the context tracking POV, preempt_schedule_irq() behaves pretty much
like an exception: It can be called anytime and schedule another task.

But currently it doesn't restore the context tracking state of the preempted
code on preempt_schedule_irq() return.

As a result, if preempt_schedule_irq() is called in the tiny frame between
user_enter() and the actual return to userspace, we resume userspace with
the wrong context tracking state.

Fix this by using exception_enter/exit() which are a perfect fit for this
kind of issue.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Mats Liljegren <mats.liljegren@enea.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      b22366cd
  13. 06 3月, 2013 7 次提交
  15. 03 3月, 2013 2 次提交
    • A
      fix compat_sys_rt_sigprocmask() · db61ec29
      由 Al Viro 提交于 
      Converting bitmask to 32bit granularity is fine, but we'd better
_do_ something with the result.  Such as "copy it to userland"...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      db61ec29
    • J
      trace/ring_buffer: handle 64bit aligned structs · 649508f6
      由 James Hogan 提交于 
      Some 32 bit architectures require 64 bit values to be aligned (for
example Meta which has 64 bit read/write instructions). These require 8
byte alignment of event data too, so use
!CONFIG_HAVE_64BIT_ALIGNED_ACCESS instead of !CONFIG_64BIT ||
CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to decide alignment, and align
buffer_data_page::data accordingly.
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org> (previous version subtly different)
      649508f6
  17. 02 3月, 2013 8 次提交
  19. 28 2月, 2013 12 次提交