* 'sched/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (76 commits)
sched_clock: and multiplier for TSC to gtod drift
sched_clock: record TSC after gtod
sched_clock: only update deltas with local reads.
sched_clock: fix calculation of other CPU
sched_clock: stop maximum check on NO HZ
sched_clock: widen the max and min time
sched_clock: record from last tick
sched: fix accounting in task delay accounting & migration
sched: add avg-overlap support to RT tasks
sched: terminate newidle balancing once at least one task has moved over
sched: fix warning
sched: build fix
sched: sched_clock_cpu() based cpu_clock(), lockdep fix
sched: export cpu_clock
sched: make sched_{rt,fair}.c ifdefs more readable
sched: bias effective_load() error towards failing wake_affine().
sched: incremental effective_load()
sched: correct wakeup weight calculations
sched: fix mult overflow
sched: update shares on wakeup
...
Working with ftrace I would get large jumps of 11 millisecs or more with
the clock tracer. This killed the latencing timings of ftrace and also
caused the irqoff self tests to fail.
What was happening is with NO_HZ the idle would stop the jiffy counter and
before the jiffy counter was updated the sched_clock would have a bad
delta jiffies to compare with the gtod with the maximum.
The jiffies would stop and the last sched_tick would record the last gtod.
On wakeup, the sched clock update would compare the gtod + delta jiffies
(which would be zero) and compare it to the TSC. The TSC would have
correctly (with a stable TSC) moved forward several jiffies. But because the
jiffies has not been updated yet the clock would be prevented from moving
forward because it would appear that the TSC jumped too far ahead.
The clock would then virtually stop, until the jiffies are updated. Then
the next sched clock update would see that the clock was very much behind
since the delta jiffies is now correct. This would then jump the clock
forward by several jiffies.
This caused ftrace to report several milliseconds of interrupts off
latency at every resume from NO_HZ idle.
This patch adds hooks into the nohz code to disable the checking of the
maximum clock update when nohz is in effect. It resumes the max check
when nohz has updated the jiffies again.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
C1E on AMD machines is like C3 but without control from the OS. Up to
now we disabled the local apic timer for those machines as it stops
when the CPU goes into C1E. This excludes those machines from high
resolution timers / dynamic ticks, which hurts especially X2 based
laptops.
The current boot time C1E detection has another, more serious flaw
as well: some BIOSes do not enable C1E until the ACPI processor module
is loaded. This causes systems to stop working after that point.
To work nicely with C1E enabled machines we use a separate idle
function, which checks on idle entry whether C1E was enabled in the
Interrupt Pending Message MSR. This allows us to do timer broadcasting
for C1E and covers the late enablement of C1E as well.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
File permissions for
/sys/devices/system/clocksource/clocksource0/available_clocksource
are 600 which allows write access. But this is in fact a read only
file. So change permissions to 400.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Remove the leap second handling from second_overflow(), which doesn't have to
check for it every second anymore. With CONFIG_NO_HZ this also makes sure the
leap second is handled close to the full second. Additionally this makes it
possible to abort a leap second properly by resetting the STA_INS/STA_DEL
status bits.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
time_offset is already a 64bit value but its resolution barely used, so this
makes better use of it by replacing SHIFT_UPDATE with TICK_LENGTH_SHIFT.
Side note: the SHIFT_HZ in SHIFT_UPDATE was incorrect for CONFIG_NO_HZ and the
primary reason for changing time_offset to 64bit to avoid the overflow.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This changes time_freq to a 64bit value and makes it static (the only outside
user had no real need to modify it). Intermediate values were already 64bit,
so the change isn't that big, but it saves a little in shifts by replacing
SHIFT_NSEC with TICK_LENGTH_SHIFT. PPM_SCALE is then used to convert between
user space and kernel space representation.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This adds a few more things from the ntp nanokernel related to user space.
It's now possible to select the resolution used of some values via STA_NANO
and the kernel reports in which mode it works (pll/fll).
If some values for adjtimex() are outside the acceptable range, they are now
simply normalized instead of letting the syscall fail. I removed
MOD_CLKA/MOD_CLKB as the mapping didn't really makes any sense, the kernel
doesn't support setting the clock.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
x86 is the only arch right now, which provides an optimized for
div_long_long_rem and it has the downside that one has to be very careful that
the divide doesn't overflow.
The API is a little akward, as the arguments for the unsigned divide are
signed. The signed version also doesn't handle a negative divisor and
produces worse code on 64bit archs.
There is little incentive to keep this API alive, so this converts the few
users to the new API.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
David Miller reported:
|--------------->
the following commit:
| commit 27ec440779
| Author: Ingo Molnar <mingo@elte.hu>
| Date: Thu Feb 28 21:00:21 2008 +0100
|
| sched: make cpu_clock() globally synchronous
|
| Alexey Zaytsev reported (and bisected) that the introduction of
| cpu_clock() in printk made the timestamps jump back and forth.
|
| Make cpu_clock() more reliable while still keeping it fast when it's
| called frequently.
|
| Signed-off-by: Ingo Molnar <mingo@elte.hu>
causes watchdog triggers when a cpu exits NOHZ state when it has been
there for >= the soft lockup threshold, for example here are some
messages from a 128 cpu Niagara2 box:
[ 168.106406] BUG: soft lockup - CPU#11 stuck for 128s! [dd:3239]
[ 168.989592] BUG: soft lockup - CPU#21 stuck for 86s! [swapper:0]
[ 168.999587] BUG: soft lockup - CPU#29 stuck for 91s! [make:4511]
[ 168.999615] BUG: soft lockup - CPU#2 stuck for 85s! [swapper:0]
[ 169.020514] BUG: soft lockup - CPU#37 stuck for 91s! [swapper:0]
[ 169.020514] BUG: soft lockup - CPU#45 stuck for 91s! [sh:4515]
[ 169.020515] BUG: soft lockup - CPU#69 stuck for 92s! [swapper:0]
[ 169.020515] BUG: soft lockup - CPU#77 stuck for 92s! [swapper:0]
[ 169.020515] BUG: soft lockup - CPU#61 stuck for 92s! [swapper:0]
[ 169.112554] BUG: soft lockup - CPU#85 stuck for 92s! [swapper:0]
[ 169.112554] BUG: soft lockup - CPU#101 stuck for 92s! [swapper:0]
[ 169.112554] BUG: soft lockup - CPU#109 stuck for 92s! [swapper:0]
[ 169.112554] BUG: soft lockup - CPU#117 stuck for 92s! [swapper:0]
[ 169.171483] BUG: soft lockup - CPU#40 stuck for 80s! [dd:3239]
[ 169.331483] BUG: soft lockup - CPU#13 stuck for 86s! [swapper:0]
[ 169.351500] BUG: soft lockup - CPU#43 stuck for 101s! [dd:3239]
[ 169.531482] BUG: soft lockup - CPU#9 stuck for 129s! [mkdir:4565]
[ 169.595754] BUG: soft lockup - CPU#20 stuck for 93s! [swapper:0]
[ 169.626787] BUG: soft lockup - CPU#52 stuck for 93s! [swapper:0]
[ 169.626787] BUG: soft lockup - CPU#84 stuck for 92s! [swapper:0]
[ 169.636812] BUG: soft lockup - CPU#116 stuck for 94s! [swapper:0]
It's simple enough to trigger this by doing a 10 minute sleep after a
fresh bootup then starting a parallel kernel build.
I suspect this might be reintroducing a problem we've had and fixed
before, see the thread:
http://marc.info/?l=linux-kernel&m=119546414004065&w=2
<---------------|
touch the softlockup watchdog when exiting NOHZ state - we are
obviously not locked up.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-hrt:
hrtimer: optimize the softirq time optimization
hrtimer: reduce calls to hrtimer_get_softirq_time()
clockevents: fix typo in tick-broadcast.c
jiffies: add time_is_after_jiffies and others which compare with jiffies
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched-devel: (62 commits)
sched: build fix
sched: better rt-group documentation
sched: features fix
sched: /debug/sched_features
sched: add SCHED_FEAT_DEADLINE
sched: debug: show a weight tree
sched: fair: weight calculations
sched: fair-group: de-couple load-balancing from the rb-trees
sched: fair-group scheduling vs latency
sched: rt-group: optimize dequeue_rt_stack
sched: debug: add some debug code to handle the full hierarchy
sched: fair-group: SMP-nice for group scheduling
sched, cpuset: customize sched domains, core
sched, cpuset: customize sched domains, docs
sched: prepatory code movement
sched: rt: multi level group constraints
sched: task_group hierarchy
sched: fix the task_group hierarchy for UID grouping
sched: allow the group scheduler to have multiple levels
sched: mix tasks and groups
...
Various SMP balancing algorithms require that the bandwidth period
run in sync.
Possible improvements are moving the rt_bandwidth thing into root_domain
and keeping a span per rt_bandwidth which marks throttled cpus.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We already catch most of the TSC problems by sanity checks, but there
is a subtle bug which has been in the code forever. This can cause
time jumps in the range of hours.
This was reported in:
http://lkml.org/lkml/2007/8/23/96
and
http://lkml.org/lkml/2008/3/31/23
I was able to reproduce the problem with a gettimeofday loop test on a
dual core and a quad core machine which both have sychronized
TSCs. The TSCs seems not to be perfectly in sync though, but the
kernel is not able to detect the slight delta in the sync check. Still
there exists an extremly small window where this delta can be observed
with a real big time jump. So far I was only able to reproduce this
with the vsyscall gettimeofday implementation, but in theory this
might be observable with the syscall based version as well.
CPU 0 updates the clock source variables under xtime/vyscall lock and
CPU1, where the TSC is slighty behind CPU0, is reading the time right
after the seqlock was unlocked.
The clocksource reference data was updated with the TSC from CPU0 and
the value which is read from TSC on CPU1 is less than the reference
data. This results in a huge delta value due to the unsigned
subtraction of the TSC value and the reference value. This algorithm
can not be changed due to the support of wrapping clock sources like
pm timer.
The huge delta is converted to nanoseconds and added to xtime, which
is then observable by the caller. The next gettimeofday call on CPU1
will show the correct time again as now the TSC has advanced above the
reference value.
To prevent this TSC specific wreckage we need to compare the TSC value
against the reference value and return the latter when it is larger
than the actual TSC value.
I pondered to mark the TSC unstable when the readout is smaller than
the reference value, but this would render an otherwise good and fast
clocksource unusable without a real good reason.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* git://git.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-hrt:
clocksource: make clocksource watchdog cycle through online CPUs
Documentation: move timer related documentation to a single place
clockevents: optimise tick_nohz_stop_sched_tick() a bit
locking: remove unused double_spin_lock()
hrtimers: simplify lockdep handling
timers: simplify lockdep handling
posix-timers: fix shadowed variables
timer_list: add annotations to workqueue.c
hrtimer: use nanosleep specific restart_block fields
hrtimer: add nanosleep specific restart_block member
In order to not trip the clocksource watchdog, kgdb must touch the
clocksource watchdog on the return to normal system run state.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
