ARM: 7011/1: Add ARM cpu topology definition

The affinity between ARM processors is defined in the MPIDR register.
We can identify which processors are in the same cluster,
and which ones have performance interdependency. We can define the
cpu topology of ARM platform, that is then used by sched_mc and sched_smt.

The default state of sched_mc and sched_smt config is disable.
When enabled, the behavior of the scheduler can be modified with
sched_mc_power_savings and sched_smt_power_savings sysfs interfaces.

Changes since v4 :
*  Remove unnecessary parentheses and blank lines

Changes since v3 :
* Update the format of printk message
* Remove blank line

Changes since v2 :
* Update the commit message and some comments

Changes since v1 :
* Update the commit message
* Add read_cpuid_mpidr in arch/arm/include/asm/cputype.h
* Modify header of arch/arm/kernel/topology.c
* Modify tests and manipulation of MPIDR's bitfields
* Modify the place and dependancy of the config
* Modify Noop functions

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: 7182/1: ARM cpu topology: fix warning

kernel/sched.c:7354:2: warning: initialization from incompatible pointer type

Align cpu_coregroup_mask prototype interface with sched_domain_mask_f typedef
use int cpu instead of unsigned int cpu

Cc: <stable@vger.kernel.org>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
sched: Ensure cpu_power periodic update

With a lot of small tasks, the softirq sched is nearly never called
when no_hz is enabled. In this case load_balance() is mainly called
with the newly_idle mode which doesn't update the cpu_power.

Add a next_update field which ensure a maximum update period when
there is short activity.

Having stale cpu_power information can skew the load-balancing
decisions, this is cured by the guaranteed update.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1323717668-2143-1-git-send-email-vincent.guittot@linaro.org
ARM: topology: save cpu id of each core
ARM: topology: Update topology according to current sched_mc mode
ARM: topology: Add a cpu_power function
ARM: topology: Add a topology update notification
ARM: cpu topology: Add asym topology flag for using cpu0 1st

Modify the CPU sched_domain flags in powersave mode for using the cpu0 in ched_mc powersave mode

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
ARM: cpu topology: add debugfs
cpupower: update the cpu_power according to cpu load

This driver updates the capacity of each core according to current
sched_mc level and cpu frequency (in fact current cpu load)

When the lowest frequencies are used, we are in a light load use case
and we increase the cpu capacity to keep these light tasks on CPU0

Conflicts:

	drivers/staging/Kconfig
sched: use cpu capacity to decide if a ILB is needed
pegasusq (based on ondemand): cpuidle detection

I found a problem with the ondemand governor while in earlysuspend
suspend mode (ondemand keeping the freq close to the max at all times
despite near 0% load). The problem is that the cpu starts to go in
long cpuidle cycles, a sampling_rate of 10000 (usec) is applied only
once in a while and the real sampling_rate becomes 1 second (or more).

So when a wakeup happens we return to the 10000usec sampling rate. The
ondemand sees lots of activity after the wakeup but those "loads" must
be adjusted down if the previous wall_time delta was huge and the
current one is tiny. We're too close to long cpuidle to worry about
the cpu freq anyway and it may be just a jitter load that if we take
into account without adjusting it down, will lead to the next long
cpuidle to be entered at the max freq again, and this repeats forever.

So my solution is to tweak the ondemand to scale down the "load"
according to the decrease in the wall_time delta ratio
(deep_sleep_ratio variable). This allows the CPU to stay at the lowest
freq during the deep sleeps even when the ondemand governor is enabled
and the sampling_rate is set to 10000. (setting the sampling_rate to
values >100000 would also tend to hide the problem but it'd screw the
interactive behavior by running at the lowest frequency for too long
during interactive usage)

During interactive usage with the screen on (not in earlysuspend
mode), or during playback or voip with screen off the deep_sleep_rate
is set to 1 practically all the time so it won't alter the behavior of
the ondemand governor unless the system is very idle (and in turn when
we want it to stay at low freq).

Change-Id: If0391e6d6c41c1c8c9fa590502e88e681a800b04

Signed-off-by: Andrea Arcangeli <andrea@cpushare.com>
sched/nohz: Rewrite, fix and add more accurate load-avg computation

Part 1)

After patch 453494c3d4 (sched: Fix nohz load accounting -- again!), we can fold
the idle into calc_load_tasks_idle between the last cpu load calculating and
calc_global_load calling. However problem still exits between the first cpu
load calculating and the last cpu load calculating. Every time when we do load
calculating, calc_load_tasks_idle will be added into calc_load_tasks, even if
the idle load is caused by calculated cpus. Consider following case:
5HZ+1
| cpu0_load     cpu1    cpu2    cpu3    calc_load_tasks    tasks_idle
|    1           1       1       1
|  -->calc_load                             1                  0
|    1           1       1       1
|                    -->calc_load           2                  0
|    0           0       1       0
|                    -->calc_load           2+1-3=0            -3
|    1           1       0       1
|                            -->calc_load   1-1=0              -1
V
5HZ+11     -->calc_global_load              0                  0

actually the load should be around 3, but shows nearly 0.

This can be found in our work load. The average running processes number
is about 15, but the load only shows about 4.

We provides a solution, by taking those load not calculated cpus' idle out from
global idle as calc_unmask_cpu_load_idle. Then when calc_load execute on every
cpu, we only fold calc_unmask_cpu_load_idle. After this patch, case above
should be as follow:
5HZ+1
| cpu0_load     cpu1    cpu2    cpu3   calc_load_tasks tasks_idle  unmask_idle
|    1           1       1       1
|  -->calc_load                             1              0           0
|    1           1       1       1
|              -->calc_load                 2              0           0
|    0           0       1       0
|                    -->calc_load           2+1-1=2        -3          -1
|    1           1       0       1
|                            -->calc_load   2+1=3          -2-1=-3     0
V
5HZ+11     -->calc_global_load              3              -3          0

CC: Peter Zijlstra <peterz@infradead.org>
CC: Doug Smythies <dsmythies@telus.net>
CC: Ingo Molnar <mingo@redhat.com>
CC: Tao Ma <tm@tao.ma>
CC: Sha Zhengju <handai.szj@gmail.com>
Reported-by: Sha Zhengju <handai.szj@gmail.com>
Signed-off-by: Charles Wang <muming.wq@taobao.com>

Part 2)

Thanks to Charles Wang for spotting the defects in the current code:

 - If we go idle during the sample window -- after sampling, we get a
   negative bias because we can negate our own sample.

 - If we wake up during the sample window we get a positive bias
   because we push the sample to a known active period.

So rewrite the entire nohz load-avg muck once again, now adding
copious documentation to the code.

Reported-and-tested-by: Doug Smythies <dsmythies@telus.net>
Reported-and-tested-by: Charles Wang <muming.wq@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1340373782.18025.74.camel@twins
[ minor edits ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
iosched: prevent aliased requests from starving other I/O

Hi, Jens,

If you recall, I posted an RFC patch for this back in July of last year:
http://lkml.org/lkml/2010/7/13/279

The basic problem is that a process can issue a never-ending stream of
async direct I/Os to the same sector on a device, thus starving out
other I/O in the system (due to the way the alias handling works in both
cfq and deadline).  The solution I proposed back then was to start
dispatching from the fifo after a certain number of aliases had been
dispatched.  Vivek asked why we had to treat aliases differently at all,
and I never had a good answer.  So, I put together a simple patch which
allows aliases to be added to the rb tree (it adds them to the right,
though that doesn't matter as the order isn't guaranteed anyway).  I
think this is the preferred solution, as it doesn't break up time slices
in CFQ or batches in deadline.  I've tested it, and it does solve the
starvation issue.  Let me know what you think.

Cheers,
Jeff

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

Conflicts:
	block/vr-iosched.c