Russell King reports:
| On the ARM dev boards, we have a 32-bit counter running at 24MHz. Calling
| clocks_calc_mult_shift(&mult, &shift, 24MHz, NSEC_PER_SEC, 60) gives
| us a multiplier of 2796202666 and a shift of 26.
|
| Over a large counter delta, this produces an error - lets take a count
| from 362976315 to 4280663372:
|
| (4280663372-362976315) * 2796202666 / 2^26 - (4280663372-362976315) * (1000/24)
| => -38.91872422891230269990
|
| Can we do better?
|
| (4280663372-362976315) * 2796202667 / 2^26 - (4280663372-362976315) * (1000/24)
| 19.45936211449532822051
|
| which is about twice as good as the 2796202666 multiplier.
|
| Looking at the equivalent divisions obtained, 2796202666 / 2^26 gives
| 41.66666665673255920410ns per tick, whereas 2796202667 / 2^26 gives
| 41.66666667163372039794ns. The actual value wanted is 1000/24 =
| 41.66666666666666666666ns.
Fix this by ensuring we round to nearest when calculating the
multiplier.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Tested-by: Mikael Pettersson <mikpe@it.uu.se>
Tested-by: Eric Miao <eric.y.miao@gmail.com>
Tested-by: Olof Johansson <olof@lixom.net>
Tested-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Conflicts:
MAINTAINERS
arch/arm/mach-omap2/pm24xx.c
drivers/scsi/bfa/bfa_fcpim.c
Needed to update to apply fixes for which the old branch was too
outdated.
Currently, destroy_workqueue() makes the workqueue deny all new
queueing by setting WQ_DYING and flushes the workqueue once before
proceeding with destruction; however, there are cases where work items
queue more related work items. Currently, such users need to
explicitly flush the workqueue multiple times depending on the
possible depth of such chained queueing.
This patch updates the queueing path such that a work item can queue
further work items on the same workqueue even when WQ_DYING is set.
The flush on destruction is automatically retried until the workqueue
is empty. This guarantees that the workqueue is empty on destruction
while allowing chained queueing.
The flush retry logic whines if it takes too many retries to drain the
workqueue.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
x86-32: Make sure we can map all of lowmem if we need to
x86, vt-d: Handle previous faults after enabling fault handling
x86: Enable the intr-remap fault handling after local APIC setup
x86, vt-d: Fix the vt-d fault handling irq migration in the x2apic mode
x86, vt-d: Quirk for masking vtd spec errors to platform error handling logic
x86, xsave: Use alloc_bootmem_align() instead of alloc_bootmem()
bootmem: Add alloc_bootmem_align()
x86, gcc-4.6: Use gcc -m options when building vdso
x86: HPET: Chose a paranoid safe value for the ETIME check
x86: io_apic: Avoid unused variable warning when CONFIG_GENERIC_PENDING_IRQ=n
* 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
perf: Fix off by one in perf_swevent_init()
perf: Fix duplicate events with multiple-pmu vs software events
ftrace: Have recordmcount honor endianness in fn_ELF_R_INFO
scripts/tags.sh: Add magic for trace-events
tracing: Fix panic when lseek() called on "trace" opened for writing
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: Fix the irqtime code for 32bit
sched: Fix the irqtime code to deal with u64 wraps
nohz: Fix get_next_timer_interrupt() vs cpu hotplug
Sched: fix skip_clock_update optimization
sched: Cure more NO_HZ load average woes
Mike Galbraith reported poor interactivity[*] when the new shares distribution
code was combined with autogroups.
The root cause turns out to be a mis-ordering of accounting accrued execution
time and shares updates. Since update_curr() is issued hierarchically,
updating the parent entity weights to reflect child enqueue/dequeue results in
the parent's unaccounted execution time then being accrued (vs vruntime) at the
new weight as opposed to the weight present at accumulation.
While this doesn't have much effect on processes with timeslices that cross a
tick, it is particularly problematic for an interactive process (e.g. Xorg)
which incurs many (tiny) timeslices. In this scenario almost all updates are
at dequeue which can result in significant fairness perturbation (especially if
it is the only thread, resulting in potential {tg->shares, MIN_SHARES}
transitions).
Correct this by ensuring unaccounted time is accumulated prior to manipulating
an entity's weight.
[*] http://xkcd.com/619/ is perversely Nostradamian here.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20101216031038.159704378@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Long running entities that do not block (dequeue) require periodic updates to
maintain accurate share values. (Note: group entities with several threads are
quite likely to be non-blocking in many circumstances).
By virtue of being long-running however, we will see entity ticks (otherwise
the required update occurs in dequeue/put and we are done). Thus we can move
the detection (and associated work) for these updates into the periodic path.
This restores the 'atomicity' of update_curr() with respect to accounting.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101216031038.067028969@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6:
x86: avoid high BIOS area when allocating address space
x86: avoid E820 regions when allocating address space
x86: avoid low BIOS area when allocating address space
resources: add arch hook for preventing allocation in reserved areas
Revert "resources: support allocating space within a region from the top down"
Revert "PCI: allocate bus resources from the top down"
Revert "x86/PCI: allocate space from the end of a region, not the beginning"
Revert "x86: allocate space within a region top-down"
Revert "PCI: fix pci_bus_alloc_resource() hang, prefer positive decode"
PCI: Update MCP55 quirk to not affect non HyperTransport variants
The irq work queue is a per cpu object and it is sufficient for
synchronization if per cpu atomics are used. Doing so simplifies
the code and reduces the overhead of the code.
Before:
christoph@linux-2.6$ size kernel/irq_work.o
text data bss dec hex filename
451 8 1 460 1cc kernel/irq_work.o
After:
christoph@linux-2.6$ size kernel/irq_work.o
text data bss dec hex filename
438 8 1 447 1bf kernel/irq_work.o
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Christoph Lameter <cl@linux.com>
When the current __call_rcu() function was written, the expedited
APIs did not exist. The __call_rcu() implementation therefore went
to great lengths to detect the end of old grace periods and to start
new ones, all in the name of reducing grace-period latency. Now the
expedited APIs do exist, and the usage of __call_rcu() has increased
considerably. This commit therefore causes __call_rcu() to avoid
worrying about grace periods unless there are a large number of
RCU callbacks stacked up on the current CPU.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Some recent benchmarks have indicated possible lock contention on the
leaf-level rcu_node locks. This commit therefore limits the number of
CPUs per leaf-level rcu_node structure to 16, in other words, there
can be at most 16 rcu_data structures fanning into a given rcu_node
structure. Prior to this, the limit was 32 on 32-bit systems and 64 on
64-bit systems.
Note that the fanout of non-leaf rcu_node structures is unchanged. The
organization of accesses to the rcu_node tree is such that references
to non-leaf rcu_node structures are much less frequent than to the
leaf structures.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Use the CPU's bit in rnp->qsmask to determine whether or not the CPU
should try to report a quiescent state. Handle overflow in the check
for rdp->gpnum having fallen behind.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
When a CPU that was in an extended quiescent state wakes
up and catches up with grace periods that remote CPUs
completed on its behalf, we update the completed field
but not the gpnum that keeps a stale value of a backward
grace period ID.
Later, note_new_gpnum() will interpret the shift between
the local CPU and the node grace period ID as some new grace
period to handle and will then start to hunt quiescent state.
But if every grace periods have already been completed, this
interpretation becomes broken. And we'll be stuck in clusters
of spurious softirqs because rcu_report_qs_rdp() will make
this broken state run into infinite loop.
The solution, as suggested by Lai Jiangshan, is to ensure that
the gpnum and completed fields are well synchronized when we catch
up with completed grace periods on their behalf by other cpus.
This way we won't start noting spurious new grace periods.
Suggested-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
When a CPU is idle and others CPUs handled its extended
quiescent state to complete grace periods on its behalf,
it will catch up with completed grace periods numbers
when it wakes up.
But at this point there might be no more grace period to
complete, but still the woken CPU always keeps its stale
qs_pending value and will then continue to chase quiescent
states even if its not needed anymore.
This results in clusters of spurious softirqs until a new
real grace period is started. Because if we continue to
chase quiescent states but we have completed every grace
periods, rcu_report_qs_rdp() is puzzled and makes that
state run into infinite loops.
As suggested by Lai Jiangshan, just reset qs_pending if
someone completed every grace periods on our behalf.
Suggested-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The fix in commit #6a0cc49 requires more than three concurrent instances
of synchronize_sched_expedited() before batching is possible. This
patch uses a ticket-counter-like approach that is also not unrelated to
Lai Jiangshan's Ring RCU to allow sharing of expedited grace periods even
when there are only two concurrent instances of synchronize_sched_expedited().
This commit builds on Tejun's original posting, which may be found at
http://lkml.org/lkml/2010/11/9/204, adding memory barriers, avoiding
overflow of signed integers (other than via atomic_t), and fixing the
detection of batching.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This adds arch_remove_reservations(), which an arch can implement if it
needs to protect part of the address space from allocation.
Sometimes that can be done by just putting a region in the resource tree,
but there are cases where that doesn't work well. For example, x86 BIOS
E820 reservations are not related to devices, so they may overlap part of,
all of, or more than a device resource, so they may not end up at the
correct spot in the resource tree.
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Use this_cpu_inc_return in one place and avoid ugly __raw_get_cpu in
another.
V3->V4:
- Fix off by one.
V4-V4f:
- Use &listener_array
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
__get_cpu_var() can be replaced with this_cpu_read and will then use a
single read instruction with implied address calculation to access the
correct per cpu instance.
However, the address of a per cpu variable passed to __this_cpu_read()
cannot be determined (since it's an implied address conversion through
segment prefixes). Therefore apply this only to uses of __get_cpu_var
where the address of the variable is not used.
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
tty: add 'active' sysfs attribute to tty0 and console device
Userspace can query the actual virtual console, and the configured
console devices behind /dev/tt0 and /dev/console.
The last entry in the list of devices is the active device, analog
to the console= kernel command line option.
The attribute supports poll(), which is raised when the virtual
console is changed or /dev/console is reconfigured.
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
index 0000000..b138b66
Commit 3624eb0 (PM / Hibernate: Modify signature used to mark swap)
attempted to modify hibernate signature used to mark swap partitions
containing hibernation images, so that old kernels don't try to
handle compressed images. However, this change broke resume from
hibernation on Fedora 14 that apparently doesn't pass the resume=
argument to the kernel and tries to trigger resume from early user
space. This doesn't work, because the signature is now different,
so the old signature has to be restored to avoid the problem.
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=22732 .
Reported-by: Dr. David Alan Gilbert <linux@treblig.org>
Reported-by: Zhang Rui <rui.zhang@intel.com>
Reported-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The user-space hibernation sends a wrong notification after the image
restoration because of thinko for the file flag check. RDONLY
corresponds to hibernation and WRONLY to restoration, confusingly.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: stable@kernel.org
Simple sysfs emumeration of the PMUs.
Use a "event_source" bus, and add PMU devices using their name.
Each PMU device has a type attribute which contrains the value needed
for perf_event_attr::type to identify this PMU.
This is the minimal stub needed to start using this interface,
we'll consider extending the sysfs usage later.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101117222056.316982569@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Extend the perf_pmu_register() interface to allow for named and
dynamic pmu types.
Because we need to support the existing static types we cannot use
dynamic types for everything, hence provide a type argument.
If we want to enumerate the PMUs they need a name, provide one.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101117222056.259707703@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Since the irqtime accounting is using non-atomic u64 and can be read
from remote cpus (writes are strictly cpu local, reads are not) we
have to deal with observing partial updates.
When we do observe partial updates the clock movement (in particular,
->clock_task movement) will go funny (in either direction), a
subsequent clock update (observing the full update) will make it go
funny in the oposite direction.
Since we rely on these clocks to be strictly monotonic we cannot
suffer backwards motion. One possible solution would be to simply
ignore all backwards deltas, but that will lead to accounting
artefacts, most notable: clock_task + irq_time != clock, this
inaccuracy would end up in user visible stats.
Therefore serialize the reads using a seqcount.
Reviewed-by: Venkatesh Pallipadi <venki@google.com>
Reported-by: Mikael Pettersson <mikpe@it.uu.se>
Tested-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1292242434.6803.200.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Some ARM systems have a short sched_clock() [ which needs to be fixed
too ], but this exposed a bug in the irq_time code as well, it doesn't
deal with wraps at all.
Fix the irq_time code to deal with u64 wraps by re-writing the code to
only use delta increments, which avoids the whole issue.
Reviewed-by: Venkatesh Pallipadi <venki@google.com>
Reported-by: Mikael Pettersson <mikpe@it.uu.se>
Tested-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1292242433.6803.199.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The perf_swevent_enabled[] array has PERF_COUNT_SW_MAX elements.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101024195041.GT5985@bicker>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: It is likely that WORKER_NOT_RUNNING is true
MAINTAINERS: Add workqueue entry
workqueue: check the allocation of system_unbound_wq
If you try to build a kernel with KCONFIG_CONFIG set (to a value
not equal to .config) and that config sets CONFIG_IKCONFIG then the
build will fail with:
make[1]: *** No rule to make target `.config', needed by \
`kernel/config_data.gz'. Stop.
because the kernel/Makefile contains a direct reference to .config.
This issue has been present since the introduction of KCONFIG_CONFIG
in 14cdd3c402.
Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
CC: Roman Zippel <zippel@linux-m68k.org>
CC: Michal Marek <mmarek@suse.cz>
Reviewed-by: Michal Marek <mmarek@suse.cz>
Signed-off-by: Michal Marek <mmarek@suse.cz>
Running the annotate branch profiler on three boxes, including my
main box that runs firefox, evolution, xchat, and is part of the distcc farm,
showed this with the likelys in the workqueue code:
correct incorrect % Function File Line
------- --------- - -------- ---- ----
96 996253 99 wq_worker_sleeping workqueue.c 703
96 996247 99 wq_worker_waking_up workqueue.c 677
The likely()s in this case were assuming that WORKER_NOT_RUNNING will
most likely be false. But this is not the case. The reason is
(and shown by adding trace_printks and testing it) that most of the time
WORKER_PREP is set.
In worker_thread() we have:
worker_clr_flags(worker, WORKER_PREP);
[ do work stuff ]
worker_set_flags(worker, WORKER_PREP, false);
(that 'false' means not to wake up an idle worker)
The wq_worker_sleeping() is called from schedule when a worker thread
is putting itself to sleep. Which happens most of the time outside
of that [ do work stuff ].
The wq_worker_waking_up is called by the wakeup worker code, which
is also callod outside that [ do work stuff ].
Thus, the likely and unlikely used by those two functions are actually
backwards.
Remove the annotation and let gcc figure it out.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
The unlikely() used in ttwu_post_activation() tests if the rq->idle_stamp
is set. But since this is for a wakeup, and wakeups happen when tasks
block on IO, and blocking tasks on IO may put the system into idle,
this can actually be a common occurence.
Running the annotated branch profiler on an average desktop running
firefox, evolution, xchat and distcc, the report shows:
correct incorrect % Function File Line
------- --------- - -------- ---- ----
34884862 146110926 80 ttwu_post_activation sched.c 2309
80% of the time, this unlikely is incorrect. Best not to assume what the
result is, and just remove the branch annotation.
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The rt_policy() has an unlikely() that the policy it is checking is
of RT priority (SCHED_FIFO or SCHED_RR).
According to the annotate branch profiler it is incorrect most of the time:
correct incorrect % Function File Line
------- --------- - -------- ---- ----
36667 654674 94 rt_policy sched.c 126
This makes sense because the rt_policy() is used by the sched_set_scheduler()
and nice(). Although users may use sys_nice a bit, all RT users use
the sched_set_scheduler() to set their RT priority, including kernel
threads.
The above numbers were from a normal desktop computer running
firefox, evolution, xchat and was part of a distcc compile farm.
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The if (unlikely(!rt_rq->rt_nr_running)) test in pick_next_task_rt()
tests if there is another rt task ready to run. If so, then pick it.
In most systems, only one RT task runs at a time most of the time.
Running the branch unlikely annotator profiler on a system doing average
work "running firefox, evolution, xchat, distcc builds, etc", it showed the
following:
correct incorrect % Function File Line
------- --------- - -------- ---- ----
324344 135104992 99 _pick_next_task_rt sched_rt.c 1064
99% of the time the condition is true. When an RT task schedules out,
it is unlikely that another RT task is waiting to run on that same run queue.
Simply remove the unlikely() condition.
Acked-by: Gregory Haskins <ghaskins@novell.com>
Cc:Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
During suspend, we disable all the non boot cpus. And during resume we bring
them all back again. So no need to do alternatives_smp_switch() in between.
On my core 2 based laptop, this speeds up the suspend path by 15msec and the
resume path by 5 msec (suspend/resume speed up differences can be attributed
to the different P-states that the cpu is in during suspend/resume).
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1290557500.4946.8.camel@sbsiddha-MOBL3.sc.intel.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Since [commit 9a897c5a:
sched: RT-balance, replace hooks with pre/post schedule and wakeup methods]
we must call pre_schedule_rt if prev is rt task.
So condition rt_task(prev) is always true and the 'unlikely' declaration is
simply incorrect.
Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
In converting the hrtimers to timerqueue, I missed
a spot in hrtimer_run_queues where we loop running
timers. We end up not pulling the new next value out
and instead just use the last next value, causing
boot time hangs in some cases.
The proper fix is to pull timerqueue_getnext each iteration
instead of using a local next value.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: John Stultz <john.stultz@linaro.org>
