kernel news – 23.04.2013

Posted: April 23, 2013 in kernel

-Nicolas Ferre and at91:

Another (late) round of SoC patches for 3.10 (or, of course 3.11). I would
totally understand if you delay this series to 3.11 as the merge window is
opening in one week.

I decided to sent this pull-request to you because it deals with the common
slave DMA bindings for AT91 SoCs. It is a long-awaited feature and it can be
interesting to see it merged as soon as possible.

The last patch is not related to DMA bindings but is pretty trivial.

Tell me what you think about this…
Thanks, best regards,

-Frederic Weisbecker has linux-dynticks updates:

Ingo,

Please pull the latest full dynticks branch that can found at:

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
timers/nohz

HEAD: 67826eae8c16dbf00c262be6ec15021bb42f69c4

This handles perf and CPUs that get more than one task and fix posix cpu timers
handling.

This can finally stop the tick. It boots and doesn’t crash, as far as I tested.

Now what’s left:

* Kick CPUs’ tick when the clock is marked unstable

* Kick CPUs when they extend the RCU grace periods too much by staying in
the kernel for too long (we are discussing this with Paul).

* sched_class:task_tick(). There are gazillions statistics maintained there.
It’s probably mostly about local and global fairness. May be for other stuff
too (cgroups, etc…).

* update_cpu_load_active(): again, various stats maintained there

* load balancing (see trigger_load_balance() usually called from the tick).

I hope we can handle these things progressively in the long run.

Thanks.

-The same Frederic comes back with a dynticks, namely timers/nohz call
for testers:

This is on top of my previous pull request (the timers/nohz branch) and
it is deemed to ease testing and help to diagnose failures:

* First patch enables CONFIG_RCU_NOCB_ALL when we have full dynticks to
ease automatic testing of the feature. This should also further
help simplifying the code. If users want more granularity in the future
to set RCU nocbs and timekeeper masks, we can still step back and
select CONFIG_RCU_NOCB_ALL only when we have CONFIG_NO_HZ_FULL_ALL.
Note this will only have an effect on tip/master because that config
is in core/rcu and not yet upstream.

* Second patch adds some tracepoints to dump the dynticks behaviour as
I got many questions from user who don’t know how to diagnose why the
tick didn’t stop on their settings.

Thanks.

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