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>
mm: slub: Default slub_max_order to 0

To avoid locking and per-cpu overhead, SLUB optimisically uses
high-order allocations up to order-3 by default and falls back to
lower allocations if they fail. While care is taken that the caller
and kswapd take no unusual steps in response to this, there are
further consequences like shrinkers who have to free more objects to
release any memory. There is anecdotal evidence that significant time
is being spent looping in shrinkers with insufficient progress being
made (https://lkml.org/lkml/2011/4/28/361) and keeping kswapd awake.

SLUB is now the default allocator and some bug reports have been
pinned down to SLUB using high orders during operations like
copying large amounts of data. SLUBs use of high-orders benefits
applications that are sized to memory appropriately but this does not
necessarily apply to large file servers or desktops.  This patch
causes SLUB to use order-0 pages like SLAB does by default.
There is further evidence that this keeps kswapd's usage lower
(https://lkml.org/lkml/2011/5/10/383).

Signed-off-by: Mel Gorman <mgorman@suse.de>
locking: Various static lock initializer fixes

The static lock initializers want to be fed the proper name of the
lock and not some random string. In mainline random strings are
obfuscating the readability of debug output, but for RT they prevent
the spinlock substitution. Fix it up.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diag: Add new polling command

Diag driver should now support a new polling command for the tools
to recognize the target.

Change-Id: Ia7966cc74c5c74693cebfd64b178831e5ca6f2dd
Signed-off-by: Ravi Aravamudhan <aravamud@codeaurora.org>
msm: kgsl: Use high priority workqueue

Signed-off-by: Luka Karinja <lk@varjanta.com>
futex: Misc cleanups

Date	Thu, 2 Jan 2014 07:05:17 -0800

From: Jason Low <jason.low2@hp.com>

- Remove unnecessary head variables.
- Delete unused parameter in queue_unlock().

Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Scott Norton <scott.norton@hp.com>
Cc: Tom Vaden <tom.vaden@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>
futex: Larger hash table

Date	Thu, 2 Jan 2014 07:05:18 -0800

From: Davidlohr Bueso <davidlohr@hp.com>

Currently, the futex global hash table suffers from it's fixed, smallish
(for today's standards) size of 256 entries, as well as its lack of NUMA
awareness. Large systems, using many futexes, can be prone to high amounts
of collisions; where these futexes hash to the same bucket and lead to
extra contention on the same hb->lock. Furthermore, cacheline bouncing is a
reality when we have multiple hb->locks residing on the same cacheline and
different futexes hash to adjacent buckets.
This patch keeps the current static size of 16 entries for small systems,
or otherwise, 256 * ncpus (or larger as we need to round the number to a
power of 2). Note that this number of CPUs accounts for all CPUs that can
ever be available in the system, taking into consideration things like
hotpluging. While we do impose extra overhead at bootup by making the hash
table larger, this is a one time thing, and does not shadow the benefits
of this patch.

Furthermore, as suggested by tglx, by cache aligning the hash buckets we can
avoid access across cacheline boundaries and also avoid massive cache line
bouncing if multiple cpus are hammering away at different hash buckets which
happen to reside in the same cache line.

Also, similar to other core kernel components (pid, dcache, tcp), by using
alloc_large_system_hash() we benefit from its NUMA awareness and thus the
table is distributed among the nodes instead of in a single one.

For a custom microbenchmark that pounds on the uaddr hashing -- making the wait
path fail at futex_wait_setup() returning -EWOULDBLOCK for large amounts of
futexes, we can see the following benefits on a 80-core, 8-socket 1Tb server:

+---------+--------------------+------------------------+-----------------------+-------------------------------+
| threads | baseline (ops/sec) | aligned-only (ops/sec) | large table (ops/sec) | large table+aligned (ops/sec) |
+---------+--------------------+------------------------+-----------------------+-------------------------------+
|     512 |		 32426 | 50531  (+55.8%)	| 255274  (+687.2%)	| 292553  (+802.2%)		|
|     256 |		 65360 | 99588  (+52.3%)	| 443563  (+578.6%)	| 508088  (+677.3%)		|
|     128 |		125635 | 200075 (+59.2%)	| 742613  (+491.1%)	| 835452  (+564.9%)		|
|      80 |		193559 | 323425 (+67.1%)	| 1028147 (+431.1%)	| 1130304 (+483.9%)		|
|      64 |		247667 | 443740 (+79.1%)	| 997300  (+302.6%)	| 1145494 (+362.5%)		|
|      32 |		628412 | 721401 (+14.7%)	| 965996  (+53.7%)	| 1122115 (+78.5%)		|
+---------+--------------------+------------------------+-----------------------+-------------------------------+
Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Scott Norton <scott.norton@hp.com>
Cc: Tom Vaden <tom.vaden@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Reviewed-by: Waiman Long <Waiman.Long@hp.com>
Reviewed-and-tested-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Paul Reioux <reioux@gmail.com>
futex: Document ordering guarantees

Date	Thu, 2 Jan 2014 07:05:19 -0800

From: Thomas Gleixner <tglx@linutronix.de>

That's essential, if you want to hack on futexes.

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Darren Hart <dvhart@linux.intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Scott Norton <scott.norton@hp.com>
Cc: Tom Vaden <tom.vaden@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Waiman Long <Waiman.Long@hp.com>
Cc: Jason Low <jason.low2@hp.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Paul Reioux <reioux@gmail.com>
futex: Avoid taking hb lock if nothing to wakeup

Date	Thu, 2 Jan 2014 07:05:20 -0800

From: Davidlohr Bueso <davidlohr@hp.com>

In futex_wake() there is clearly no point in taking the hb->lock if we know
beforehand that there are no tasks to be woken. While the hash bucket's plist
head is a cheap way of knowing this, we cannot rely 100% on it as there is a
racy window between the futex_wait call and when the task is actually added to
the plist. To this end, we couple it with the spinlock check as tasks trying to
enter the critical region are most likely potential waiters that will be added
to the plist, thus preventing tasks sleeping forever if wakers don't acknowledge
all possible waiters.

Furthermore, the futex ordering guarantees are preserved, ensuring that waiters
either observe the changed user space value before blocking or is woken by a
concurrent waker. For wakers, this is done by relying on the barriers in
get_futex_key_refs() -- for archs that do have implicit mb in atomic_inc() we
explicitly add them through a new futex_get_mm function. For waiters we rely
on the fact that spin_lock calls already update the head counter, so spinners
are visible even if the lock hasn't been acquired yet.

For more details please refer to the updated comments in the code and related
discussion: https://lkml.org/lkml/2013/11/26/556

Special thanks to tglx for careful review and feedback.

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Jeff Mahoney <jeffm@suse.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Scott Norton <scott.norton@hp.com>
Cc: Tom Vaden <tom.vaden@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Waiman Long <Waiman.Long@hp.com>
Cc: Jason Low <jason.low2@hp.com>
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Paul Reioux <reioux@gmail.com>
kernel/futex.c: Linux 3.4 compatibility fix up

Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: Optimize build_sched_domains() for saving first SD node for a cpu

Date	Tue, 4 Jun 2013 16:50:18 +0530

We are saving first scheduling domain for a cpu in build_sched_domains() by
iterating over the nested sd->child list. We don't actually need to do it this
way.

*per_cpu_ptr(d.sd, i) is guaranteed to be NULL in the beginning as we have
called __visit_domain_allocation_hell() which does a memset to zero for struct
s_data.

So, save pointer to first SD while running the iteration loop over tl's.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>
ARM: fault: assume no context when IRQs are disabled during data abort.

Bail out early if IRQs are disabled in do_page_fault or else
  [14415.157266] BUG: sleeping function called from invalid context at arch/arm/mm/fault.c:301

Russell King's idea from
  http://comments.gmane.org/gmane.linux.ports.arm.omap/59256

Signed-off-by: JP Abgrall <jpa@google.com>
sched: Use cached value of span instead of calling sched_domain_span()

Date	Tue, 11 Jun 2013 16:32:43 +0530

In the beginning of build_sched_groups() we called sched_domain_span() and
cached its return value in span. Few statements later we are calling it again to
get the same pointer.

Lets use the cached value instead as it hasn't changed in between.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: don't call get_group() for covered cpus

Date	Tue, 11 Jun 2013 16:32:44 +0530

In build_sched_groups() we don't need to call get_group() for cpus which are
already covered in previous iterations. So, call get_group() after checking if
cpu is covered or not.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: remove WARN_ON(!sd) from init_sched_groups_power()

Date	Tue, 11 Jun 2013 16:32:45 +0530

sd can't be NULL in init_sched_groups_power() and so checking it for NULL isn't
useful. In case it is required, then also we need to rearrange the code a bit as
we already accessed invalid pointer sd to get sg: sg = sd->groups.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
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>
sched: scale the busy and this queue's per-task load before compare

Date	Mon, 17 Jun 2013 21:00:23 +0800

Since for max_load and this_load, they are the value that already be
scaled. It is not reasonble to get a minimum value between the scaled
and non-scaled value, like below example.
	min(sds->busiest_load_per_task, sds->max_load);

Also add comment over in what condition, there would be cpu power gain
in move the load.

Signed-off-by: Lei Wen <leiwen@marvell.com>
Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: scale cpu load for judgment of group imbalance

Date	Mon, 17 Jun 2013 21:00:24 +0800

We cannot compare two load directly from two cpus, since the cpu power
over two cpu may vary largely.

Suppose we meet such two kind of cpus.
CPU A:
	No real time work, and there are 3 task, with rq->load.weight
being 512.
CPU B:
	Has real time work, and it take 3/4 of the cpu power, which
makes CFS only take 1/4, that is 1024/4=256 cpu power. And over its CFS
runqueue, there is only one task with weight as 128.

Since both cpu's CFS task take for half of the CFS's cpu power, it
should be considered as balanced in such case.

But original judgment like:
        if ((max_cpu_load - min_cpu_load) >= avg_load_per_task &&
            (max_nr_running - min_nr_running) > 1)
It makes (512-128)>=((512+128)/4), and lead to imbalance conclusion...
Make the load as scaled, to avoid such case.

Signed-off-by: Lei Wen <leiwen@marvell.com>

modified for Mako kernel from LKML reference
Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: Reduce overestimating rq->avg_idle

Date	Thu, 29 Aug 2013 13:05:34 -0700

When updating avg_idle, if the delta exceeds some max value, then avg_idle
gets set to the max, regardless of what the previous avg was. This can cause
avg_idle to often be overestimated.

This patch modifies the way we update avg_idle by always updating it with the
function call to update_avg() first. Then, if avg_idle exceeds the max, we set
it to the max.

Signed-off-by: Jason Low <jason.low2@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: Consider max cost of idle balance per sched domain

Date    Thu, 29 Aug 2013 13:05:35 -0700

In this patch, we keep track of the max cost we spend doing idle load balancing
for each sched domain. If the avg time the CPU remains idle is less then the
time we have already spent on idle balancing + the max cost of idle balancing
in the sched domain, then we don't continue to attempt the balance. We also
keep a per rq variable, max_idle_balance_cost, which keeps track of the max
time spent on newidle load balances throughout all its domains. Additionally,
we swap sched_migration_cost used in idle_balance for rq->max_idle_balance_cost.

By using the max, we avoid overrunning the average. This further reduces the chance
we attempt balancing when the CPU is not idle for longer than the cost to balance.

I also limited the max cost of each domain to 5*sysctl_sched_migration_cost as
a way to prevent the max from becoming too inflated.

Signed-off-by: Jason Low <jason.low2@hp.com>

backported for Linux 3.4

Signed-off-by: Paul Reioux <reioux@gmail.com>