The structure cpu_isolated_map is used not only during initialization.
Multi-core scheduler configuration changes and exclusive cpusets
use this during run time.  During setting of sched_mc_power_savings
 policy, this structure is accessed to update sched_domains.
Signed-off-by: NTim Chen <tim.c.chen@intel.com>
Acked-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fix kernel-doc warnings in 2.6.20-rc1.
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Commit 2d7d2535 ("fix cond_resched() fix")
introduced an 'expected_preempt_count' parameter to __resched_legal() to
fix a bug where it was returning a false negative when called from
cond_resched_lock() and preemption was enabled.

Unfortunately this broke things for when preemption is disabled.
preempt_count() will always return zero, thus failing the check against any
value of expected_preempt_count not equal to zero.  cond_resched_lock() for
example, passes an expected_preempt_count value of 1.

So fix the fix for the cond_resched() fix by skipping the check of
preempt_count() against expected_preempt_count when preemption is disabled.

Credit should go to Sunil Mushran for spotting the bug during testing.
Signed-off-by: NMark Fasheh <mark.fasheh@oracle.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fix the schedule_on_each_cpu() implementation: __queue_work() is now
stricter, hence set the work-pending bit before passing in the new work.

(found in the -rt tree, using Peter Zijlstra's files-lock scalability
patchset)
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Problem:
  sched_fork() has always called scheduler_tick() in some (unlikely)
  circumstances in order to update the current task in light of those
  circumstances.  It has always been the case that the work done by
  scheduler_tick() was more than was required to handle the problem in
  hand but no harm was done except for the waste of a few CPU cycles.

  However, the splitting of scheduler_tick() into two procedures in
  2.6.20-rc1 enables the wasted cycles to be saved as the new procedure
  task_running_tick() does all the work that is required to rectify the
  problem being handled.

Solution:
  Replace the call to scheduler_tick() in sched_fork() with a call to
  task_running_tick().
Signed-off-by: NPeter Williams <pwil3058@bigpond.com.au>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

__set_irq_handler: Kill a bogus space
Signed-off-by: NGeert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

On architectures where the atomicity of the bit operations is handled by
external means (ie a separate spinlock to protect concurrent accesses),
just doing a direct assignment on the workqueue data field (as done by
commit 4594bf15) can cause the
assignment to be lost due to lack of serialization with the bitops on
the same word.

So we need to serialize the assignment with the locks on those
architectures (notably older ARM chips, PA-RISC and sparc32).

So rather than using an "unsigned long", let's use "atomic_long_t",
which already has a safe assignment operation (atomic_long_set()) on
such architectures.

This requires that the atomic operations use the same atomicity locks as
the bit operations do, but that is largely the case anyway.  Sparc32
will probably need fixing.

Architectures (including modern ARM with LL/SC) that implement sane
atomic operations for SMP won't see any of this matter.

Cc: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: David Miller <davem@davemloft.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Linux Arch Maintainers <linux-arch@vger.kernel.org>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

It has caused more problems than it ever really solved, and is
apparently not getting cleaned up and fixed.  We can put it back when
it's stable and isn't likely to make warning or bug events worse.

In the meantime, enable frame pointers for more readable stack traces.
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Deprecate the old "legacy" PM API, and more importantly default it to "n".
Virtually nothing in-tree uses it any more.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Show the initialization state(live, coming, going) of the module:
  $ cat /sys/module/usbcore/initstate
  live
Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Virtually index, physically tagged cache architectures can get away
without cache flushing when forking.  This patch adds a new cache
flushing function flush_cache_dup_mm(struct mm_struct *) which for the
moment I've implemented to do the same thing on all architectures
except on MIPS where it's a no-op.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

calc_load() is called by timer interrupt to update avenrun[].  It currently
calls nr_active() at each timer tick (HZ per second), while the update of
avenrun[] is done only once every 5 seconds.  (LOAD_FREQ=5 Hz)

nr_active() is quite expensive on SMP machines, since it has to sum up
nr_running and nr_uninterruptible of all online CPUS, bringing foreign
dirty cache lines.

This patch is an optimization of calc_load() so that nr_active() is called
only if we need it.

The use of unlikely() is welcome since the condition is true only once every
5*HZ time.
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: N"Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

All kcalloc() calls of the form "kcalloc(1,...)" are converted to the
equivalent kzalloc() calls, and a few kcalloc() calls with the incorrect
ordering of the first two arguments are fixed.
Signed-off-by: NRobert P. J. Day <rpjday@mindspring.com>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Adam Belay <ambx1@neo.rr.com>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Greg KH <greg@kroah.com>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Jarek Poplawski noticed that lockdep global state could be accessed in a
racy way if one CPU did a lockdep assert (shutting lockdep down), while the
other CPU would try to do something that changes its global state.

This patch fixes those races and cleans up lockdep's internal locking by
adding a graph_lock()/graph_unlock()/debug_locks_off_graph_unlock helpers.

(Also note that as we all know the Linux kernel is, by definition, bug-free
and perfect, so this code never triggers, so these fixes are highly
theoretical.  I wrote this patch for aesthetic reasons alone.)

[akpm@osdl.org: build fix]
[jarkao2@o2.pl: build fix's refix]
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NJarek Poplawski <jarkao2@o2.pl>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

When we print an assert due to scheduling-in-atomic bugs, and if lockdep
is enabled, then the IRQ tracing information of lockdep can be printed
to pinpoint the code location that disabled interrupts. This saved me
quite a bit of debugging time in cases where the backtrace did not
identify the irq-disabling site well enough.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

CONFIG_DEBUG_LOCKDEP is unacceptably slow because it does not utilize
the chain-hash. Turn the chain-hash back on in this case too.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Cleanup: the VERY_VERBOSE define was unnecessarily dependent on #ifdef VERBOSE
- while the VERBOSE switch is 0 or 1 (always defined).
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Clear all the chains during lockdep_reset().  This fixes some locking-selftest
false positives i saw on -rt.  (never saw those on mainline though, but it
could happen.)
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Make verbose lockdep messages (off by default) more informative by printing
out the hash chain key.  (this patch was what helped me catch the earlier
lockdep hash-collision bug)
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fix typo in the class_filter() function.  (filtering is not used by default so
this only affects lockdep-internal debugging cases)
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Most distributions enable sysrq support but set it to 0 by default.  Add a
sysrq_always_enabled boot option to always-enable sysrq keys.  Useful for
debugging - without having to modify the disribution's config files (which
might not be possible if the kernel is on a live CD, etc.).

Also, while at it, clean up the sysrq interfaces.

[bunk@stusta.de: make sysrq_always_enabled_setup() static]
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Currently, to tell a task that it should go to the refrigerator, we set the
PF_FREEZE flag for it and send a fake signal to it.  Unfortunately there
are two SMP-related problems with this approach.  First, a task running on
another CPU may be updating its flags while the freezer attempts to set
PF_FREEZE for it and this may leave the task's flags in an inconsistent
state.  Second, there is a potential race between freeze_process() and
refrigerator() in which freeze_process() running on one CPU is reading a
task's PF_FREEZE flag while refrigerator() running on another CPU has just
set PF_FROZEN for the same task and attempts to reset PF_FREEZE for it.  If
the refrigerator wins the race, freeze_process() will state that PF_FREEZE
hasn't been set for the task and will set it unnecessarily, so the task
will go to the refrigerator once again after it's been thawed.

To solve first of these problems we need to stop using PF_FREEZE to tell
tasks that they should go to the refrigerator.  Instead, we can introduce a
special TIF_*** flag and use it for this purpose, since it is allowed to
change the other tasks' TIF_*** flags and there are special calls for it.

To avoid the freeze_process()-refrigerator() race we can make
freeze_process() to always check the task's PF_FROZEN flag after it's read
its "freeze" flag.  We should also make sure that refrigerator() will
always reset the task's "freeze" flag after it's set PF_FROZEN for it.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Andi Kleen <ak@muc.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Currently, if a task is stopped (ie.  it's in the TASK_STOPPED state), it
is considered by the freezer as unfreezeable.  However, there may be a race
between the freezer and the delivery of the continuation signal to the task
resulting in the task running after we have finished freezing the other
tasks.  This, in turn, may lead to undesirable effects up to and including
data corruption.

To prevent this from happening we first need to make the freezer consider
stopped tasks as freezeable.  For this purpose we need to make freezeable()
stop returning 0 for these tasks and we need to force them to enter the
refrigerator.  However, if there's no continuation signal in the meantime,
the stopped tasks should remain stopped after all processes have been
thawed, so we need to send an additional SIGSTOP to each of them before
waking it up.

Also, a stopped task that has just been woken up should first check if
there's a freezing request for it and go to the refrigerator if that's the
case.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Elaborate the API for calling cpuset_zone_allowed(), so that users have to
explicitly choose between the two variants:

  cpuset_zone_allowed_hardwall()
  cpuset_zone_allowed_softwall()

Until now, whether or not you got the hardwall flavor depended solely on
whether or not you or'd in the __GFP_HARDWALL gfp flag to the gfp_mask
argument.

If you didn't specify __GFP_HARDWALL, you implicitly got the softwall
version.

Unfortunately, this meant that users would end up with the softwall version
without thinking about it.  Since only the softwall version might sleep,
this led to bugs with possible sleeping in interrupt context on more than
one occassion.

The hardwall version requires that the current tasks mems_allowed allows
the node of the specified zone (or that you're in interrupt or that
__GFP_THISNODE is set or that you're on a one cpuset system.)

The softwall version, depending on the gfp_mask, might allow a node if it
was allowed in the nearest enclusing cpuset marked mem_exclusive (which
requires taking the cpuset lock 'callback_mutex' to evaluate.)

This patch removes the cpuset_zone_allowed() call, and forces the caller to
explicitly choose between the hardwall and the softwall case.

If the caller wants the gfp_mask to determine this choice, they should (1)
be sure they can sleep or that __GFP_HARDWALL is set, and (2) invoke the
cpuset_zone_allowed_softwall() routine.

This adds another 100 or 200 bytes to the kernel text space, due to the few
lines of nearly duplicate code at the top of both cpuset_zone_allowed_*
routines.  It should save a few instructions executed for the calls that
turned into calls of cpuset_zone_allowed_hardwall, thanks to not having to
set (before the call) then check (within the call) the __GFP_HARDWALL flag.

For the most critical call, from get_page_from_freelist(), the same
instructions are executed as before -- the old cpuset_zone_allowed()
routine it used to call is the same code as the
cpuset_zone_allowed_softwall() routine that it calls now.

Not a perfect win, but seems worth it, to reduce this chance of hitting a
sleeping with irq off complaint again.
Signed-off-by: NPaul Jackson <pj@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This reverts commit 373beb35.

No one is using this identifier yet.  The purpose of this identifier is to
export nsproxy to user space which is wrong.  nsproxy is an internal
implementation optimization, which should keep our fork times from getting
slower as we increase the number of global namespaces you don't have to
share.

Adding a global identifier like this is inappropriate because it makes
namespaces inherently non-recursive, greatly limiting what we can do with
them in the future.
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Mostly changing alignment.  Just some general cleanup.

[akpm@osdl.org: build fix]
Signed-off-by: NDaniel Walker <dwalker@mvista.com>
Acked-by: NJohn Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Simply adds some ifdefs to remove clocksoure sysfs code when CONFIG_SYSFS
isn't turn on.
Signed-off-by: NDaniel Walker <dwalker@mvista.com>
Acked-by: NJohn Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Introduce a round_jiffies() function as well as a round_jiffies_relative()
function.  These functions round a jiffies value to the next whole second.
The primary purpose of this rounding is to cause all "we don't care exactly
when" timers to happen at the same jiffy.

This avoids multiple timers firing within the second for no real reason;
with dynamic ticks these extra timers cause wakeups from deep sleep CPU
sleep states and thus waste power.

The exact wakeup moment is skewed by the cpu number, to avoid all cpus from
waking up at the exact same time (and hitting the same lock/cachelines
there)

[akpm@osdl.org: fix variable type]
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

An fdtable can either be embedded inside a files_struct or standalone (after
being expanded).  When an fdtable is being discarded after all RCU references
to it have expired, we must either free it directly, in the standalone case,
or free the files_struct it is contained within, in the embedded case.

Currently the free_files field controls this behavior, but we can get rid of
it entirely, as all the necessary information is already recorded.  We can
distinguish embedded and standalone fdtables using max_fds, and if it is
embedded we can divine the relevant files_struct using container_of().
Signed-off-by: NVadim Lobanov <vlobanov@speakeasy.net>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Currently, each fdtable supports three dynamically-sized arrays of data: the
fdarray and two fdsets.  The code allows the number of fds supported by the
fdarray (fdtable->max_fds) to differ from the number of fds supported by each
of the fdsets (fdtable->max_fdset).

In practice, it is wasteful for these two sizes to differ: whenever we hit a
limit on the smaller-capacity structure, we will reallocate the entire fdtable
and all the dynamic arrays within it, so any delta in the memory used by the
larger-capacity structure will never be touched at all.

Rather than hogging this excess, we shouldn't even allocate it in the first
place, and keep the capacities of the fdarray and the fdsets equal.  This
patch removes fdtable->max_fdset.  As an added bonus, most of the supporting
code becomes simpler.
Signed-off-by: NVadim Lobanov <vlobanov@speakeasy.net>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The dup_fd() function creates a new files_struct and fdtable embedded inside
that files_struct, and then possibly expands the fdtable using expand_files().

The out_release error path is invoked when expand_files() returns an error
code.  However, when this attempt to expand fails, the fdtable is left in its
original embedded form, so it is pointless to try to free the associated
fdarray and fdsets.
Signed-off-by: NVadim Lobanov <vlobanov@speakeasy.net>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

[akpm@osdl.org: additional cleanups]
Signed-off-by: NMiguel Ojeda Sandonis <maxextreme@gmail.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

RT task does not participate in interactiveness priority and thus shouldn't
be bothered with timestamp and p->sleep_type manipulation when task is
being put on run queue.  Bypass all of the them with a single if (rt_task)
test.
Signed-off-by: NKen Chen <kenneth.w.chen@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Remove scheduler stats lb_stopbalance counter.  This counter can be
calculated by: lb_balanced - lb_nobusyg - lb_nobusyq.  There is no need to
create gazillion counters while we can derive the value.
Signed-off-by: NKen Chen <kenneth.w.chen@intel.com>
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Currently at a particular domain, each cpu in the sched group will do a
load balance at the frequency of balance_interval.  More the cores and
threads, more the cpus will be in each sched group at SMP and NUMA domain.
And we endup spending quite a bit of time doing load balancing in those
domains.

Fix this by making only one cpu(first idle cpu or first cpu in the group if
all the cpus are busy) in the sched group do the load balance at that
particular sched domain and this load will slowly percolate down to the
other cpus with in that group(when they do load balancing at lower
domains).
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Co-opt rq->timestamp_last_tick to maintain a cache_hot_time evaluation
reference timestamp at both tick and sched times to prevent said reference,
formerly rq->timestamp_last_tick, from being behind task->last_ran at
evaluation time, and to move said reference closer to current time on the
remote processor, intent being to improve cache hot evaluation and
timestamp adjustment accuracy for task migration.

Fix minor sched_time double accounting error which occurs when a task
passing through schedule() does not schedule off, and takes the next timer
tick.

[kenneth.w.chen@intel.com: cleanup]
Signed-off-by: NMike Galbraith <efault@gmx.de>
Acked-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NKen Chen <kenneth.w.chen@intel.com>
Cc: Don Mullis <dwm@meer.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Large sched domains can be very expensive to scan.  Add an option SD_SERIALIZE
to the sched domain flags.  If that flag is set then we make sure that no
other such domain is being balanced.

[akpm@osdl.org: build fix]
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Trigger softirq less frequently

We trigger the softirq before this patch using offset of sd->interval.
However, if the queue is busy then it is sufficient to schedule the softirq
with sd->interval * busy_factor.

So we modify the calculation of the next time to balance by taking
the interval added to last_balance again. This is only the
right value if the idle/busy situation continues as is.

There are two potential trouble spots:
- If the queue was idle and now gets busy then we call rebalance
  early. However, that is not a problem because we will then use
  the longer interval for the next period.

- If the queue was busy and becomes idle then we potentially
  wait too long before rebalancing. However, when the task
  goes idle then idle_balance is called. We add another calculation
  of the next balance time based on sd->interval in idle_balance
  so that we will rebalance soon.

V2->V3:
- Calculate rebalance time based on current jiffies and not
  based on the jiffies at the last time we load balanced.
  We no longer rely on staggering and therefore we can
  affort to do this now.

V3->V4:
- Use functions to do jiffy comparisons.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Call rebalance_tick (renamed to run_rebalance_domains) from a newly introduced
softirq.

We calculate the earliest time for each layer of sched domains to be rescanned
(this is the rescan time for idle) and use the earliest of those to schedule
the softirq via a new field "next_balance" added to struct rq.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>