mm: vmscan: If kswapd has been running too long, allow it to sleep

Under constant allocation pressure, kswapd can be in the situation where
sleeping_prematurely() will always return true even if kswapd has been
running a long time. Check if kswapd needs to be scheduled.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: reduce calculation effort in fix_small_imbalance

Date	Mon, 17 Jun 2013 21:00:22 +0800

Actually all below item could be repalced by scaled_busy_load_per_task
	(sds->busiest_load_per_task * SCHED_POWER_SCALE)
		/sds->busiest->sgp->power;

Signed-off-by: Lei Wen <leiwen@marvell.com>
Signed-off-by: Paul Reioux <reioux@gmail.com>
[PATCH] cpufreq: smooth scrolling (thanks to @gorkhanmoral)

Conflicts:
	arch/arm/mach-msm/cpufreq.c
sched/fair: Optimize find_busiest_queue()

Use for_each_cpu_and() and thereby avoid computing the capacity for
CPUs we know we're not interested in.

Reviewed-by: Paul Turner <pjt@google.com>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-lppceyv6kb3a19g8spmrn20b@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>

backported for Linux 3.4

Conflicts:
	kernel/sched/fair.c
sched/fair: Optimize cgroup pick_next_task_fair()

Since commit 2f36825b1 ("sched: Next buddy hint on sleep and preempt
path") it is likely we pick a new task from the same cgroup, doing a put
and then set on all intermediate entities is a waste of time, so try to
avoid this.

Measured using:

  mount nodev /cgroup -t cgroup -o cpu
  cd /cgroup
  mkdir a; cd a
  mkdir b; cd b
  mkdir c; cd c
  echo $$ > tasks
  perf stat --repeat 10 -- taskset 1 perf bench sched pipe

PRE :      4.542422684 seconds time elapsed   ( +-  0.33% )
POST:      4.389409991 seconds time elapsed   ( +-  0.32% )

Which shows a significant improvement of ~3.5%

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1328936700.2476.17.camel@laptop
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>

Backported for Linux 3.4 kernel

Conflicts:
	kernel/sched/fair.c
Bump to V2.0