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Fix this:
top - 21:54:00 up 2:59, 1 user, load average: 432512.33, 426421.74, 417432.74
Which happens because we now set TASK_WAKING before activate_task().
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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For consistencies sake, rename the argument (again).
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Clean up the code a little.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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We don't need to call update_shares() for each domain we iterate,
just got the largets one.
However, we should call it before wake_affine() as well, so that
that can use up-to-date values too.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Add back FAIR_SLEEPERS and GENTLE_FAIR_SLEEPERS.
FAIR_SLEEPERS is the old logic: credit sleepers with their sleep time.
GENTLE_FAIR_SLEEPERS dampens this a bit: 50% of their sleep time gets
credited.
The hope here is to still give the benefits of fair-sleepers logic
(quick wakeups, etc.) while not allow them to have 100% of their
sleep time as if they were running.
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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And turn it on for NUMA and MC domains. This improves
locality in balancing decisions by keeping up to
capacity amount of tasks local before looking for idle
CPUs. (and twice the capacity if SD_POWERSAVINGS_BALANCE
is set.)
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Currently we use overlap to weaken the SYNC hint, but allow it to
set the hint as well.
echo NO_SYNC_WAKEUP > /debug/sched_features
echo SYNC_MORE > /debug/sched_features
preserves pipe-test behaviour without using the WF_SYNC hint.
Worth playing with on more workloads...
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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The sync argument rename to introduce WF_* broke stuff by missing a
local alias for an argument in __wake_up_common, fix it by using
the more descriptive wake_flags name.
This restores WF_SYNC propagation, which fixes wake_affine()
behaviour, which fixes pipe-test.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Avoid the cache buddies from biasing the time distribution away
from fork()ers. Normally the next buddy will be the preferred
scheduling target, but this makes fork()s prefer to run the new
child, whereas we prefer to run the parent, since that will
generate more work.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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In order to extend the functions to have more than 1 flag (sync),
rename the argument to flags, and explicitly define a WF_ space for
individual flags.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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In order to be able to rename the sync argument, we need to rename
the current flag argument.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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I suspect a feed-back loop between cpuidle and the aperf/mperf
cpu_power bits, where when we have idle C-states lower the ratio,
which leads to lower cpu_power and then less load, which generates
more idle time, etc..
Put in a knob to disable it.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Provide an ach specific hook for cpufreq based scaling of
cpu_power.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[ego@in.ibm.com: spotting bugs]
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Make the idle balancer more agressive, to improve a
x264 encoding workload provided by Jason Garrett-Glaser:
NEXT_BUDDY NO_LB_BIAS
encoded 600 frames, 252.82 fps, 22096.60 kb/s
encoded 600 frames, 250.69 fps, 22096.60 kb/s
encoded 600 frames, 245.76 fps, 22096.60 kb/s
NO_NEXT_BUDDY LB_BIAS
encoded 600 frames, 344.44 fps, 22096.60 kb/s
encoded 600 frames, 346.66 fps, 22096.60 kb/s
encoded 600 frames, 352.59 fps, 22096.60 kb/s
NO_NEXT_BUDDY NO_LB_BIAS
encoded 600 frames, 425.75 fps, 22096.60 kb/s
encoded 600 frames, 425.45 fps, 22096.60 kb/s
encoded 600 frames, 422.49 fps, 22096.60 kb/s
Peter pointed out that this is better done via newidle_idx,
not via LB_BIAS, newidle balancing should look for where
there is load _now_, not where there was load 2 ticks ago.
Worst-case latencies are improved as well as no buddies
means less vruntime spread. (as per prior lkml discussions)
This change improves kbuild-peak parallelism as well.
Reported-by: Jason Garrett-Glaser <darkshikari@gmail.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1253011667.9128.16.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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When merging select_task_rq_fair() and sched_balance_self() we lost
the use of wake_idx, restore that and set them to 0 to make wake
balancing more aggressive.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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While merging select_task_rq_fair() and sched_balance_self() I made
a mistake that leads to testing the wrong task affinty.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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for_each_domain() uses RCU to serialize the sched_domains, except
it doesn't actually use rcu_read_lock() and instead relies on
disabling preemption -> FAIL.
XXX: audit other sched_domain code.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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One of the problems of power-saving balancing is that under certain
scenarios it is too slow and allows tons of real work to pile up.
Avoid this by ignoring the powersave stuff when there's real work
to be done.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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The problem with wake_idle() is that is doesn't respect things like
cpu_power, which means it doesn't deal well with SMT nor the recent
RT interaction.
To cure this, it needs to do what sched_balance_self() does, which
leads to the possibility of merging select_task_rq_fair() and
sched_balance_self().
Modify sched_balance_self() to:
- update_shares() when walking up the domain tree,
(it only called it for the top domain, but it should
have done this anyway), which allows us to remove
this ugly bit from try_to_wake_up().
- do wake_affine() on the smallest domain that contains
both this (the waking) and the prev (the wakee) cpu for
WAKE invocations.
Then use the top-down balance steps it had to replace wake_idle().
This leads to the dissapearance of SD_WAKE_BALANCE and
SD_WAKE_IDLE_FAR, with SD_WAKE_IDLE replaced with SD_BALANCE_WAKE.
SD_WAKE_AFFINE needs SD_BALANCE_WAKE to be effective.
Touch all topology bits to replace the old with new SD flags --
platforms might need re-tuning, enabling SD_BALANCE_WAKE
conditionally on a NUMA distance seems like a good additional
feature, magny-core and small nehalem systems would want this
enabled, systems with slow interconnects would not.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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We're going to want to drop rq->lock in try_to_wake_up() for a
longer period of time, however we also want to deal with concurrent
waking of the same task, which is currently handled by holding
rq->lock.
So introduce a new TASK state, namely TASK_WAKING, which indicates
someone is already waking the task (other wakers will fail p->state
& state).
We also keep preemption disabled over the whole ttwu().
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Rather ugly patch to fully place the sched_balance_self() code
inside the fair class.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Move the sched_balance_self() code into sched_fair.c
This facilitates the merger of sched_balance_self() and
sched_fair::select_task_rq().
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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In preparation to other code movement, move weighted_cpuload(),
source_load() and target_load() before the class includes.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Add text...
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Add a NEXT_BUDDY feature flag to aid in debugging.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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It consists of two conditions, split them out in separate toggles
so we can test them independently.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'tracing-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (105 commits)
ring-buffer: only enable ring_buffer_swap_cpu when needed
ring-buffer: check for swapped buffers in start of committing
tracing: report error in trace if we fail to swap latency buffer
tracing: add trace_array_printk for internal tracers to use
tracing: pass around ring buffer instead of tracer
tracing: make tracing_reset safe for external use
tracing: use timestamp to determine start of latency traces
tracing: Remove mentioning of legacy latency_trace file from documentation
tracing/filters: Defer pred allocation, fix memory leak
tracing: remove users of tracing_reset
tracing: disable buffers and synchronize_sched before resetting
tracing: disable update max tracer while reading trace
tracing: print out start and stop in latency traces
ring-buffer: disable all cpu buffers when one finds a problem
ring-buffer: do not count discarded events
ring-buffer: remove ring_buffer_event_discard
ring-buffer: fix ring_buffer_read crossing pages
ring-buffer: remove unnecessary cpu_relax
ring-buffer: do not swap buffers during a commit
ring-buffer: do not reset while in a commit
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (64 commits)
sched: Fix sched::sched_stat_wait tracepoint field
sched: Disable NEW_FAIR_SLEEPERS for now
sched: Keep kthreads at default priority
sched: Re-tune the scheduler latency defaults to decrease worst-case latencies
sched: Turn off child_runs_first
sched: Ensure that a child can't gain time over it's parent after fork()
sched: enable SD_WAKE_IDLE
sched: Deal with low-load in wake_affine()
sched: Remove short cut from select_task_rq_fair()
sched: Turn on SD_BALANCE_NEWIDLE
sched: Clean up topology.h
sched: Fix dynamic power-balancing crash
sched: Remove reciprocal for cpu_power
sched: Try to deal with low capacity, fix update_sd_power_savings_stats()
sched: Try to deal with low capacity
sched: Scale down cpu_power due to RT tasks
sched: Implement dynamic cpu_power
sched: Add smt_gain
sched: Update the cpu_power sum during load-balance
sched: Add SD_PREFER_SIBLING
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'perfcounters-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (60 commits)
perf tools: Avoid unnecessary work in directory lookups
perf stat: Clean up statistics calculations a bit more
perf stat: More advanced variance computation
perf stat: Use stddev_mean in stead of stddev
perf stat: Remove the limit on repeat
perf stat: Change noise calculation to use stddev
x86, perf_counter, bts: Do not allow kernel BTS tracing for now
x86, perf_counter, bts: Correct pointer-to-u64 casts
x86, perf_counter, bts: Fail if BTS is not available
perf_counter: Fix output-sharing error path
perf trace: Fix read_string()
perf trace: Print out in nanoseconds
perf tools: Seek to the end of the header area
perf trace: Fix parsing of perf.data
perf trace: Sample timestamps as well
perf_counter: Introduce new (non-)paranoia level to allow raw tracepoint access
perf trace: Sample the CPU too
perf tools: Work around strict aliasing related warnings
perf tools: Clean up warnings list in the Makefile
perf tools: Complete support for dynamic strings
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'irq-threaded-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
genirq: Do not mask oneshot edge type interrupts
genirq: Support nested threaded irq handling
genirq: Add buslock support
genirq: Add oneshot support
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
pci/intr_remapping: Allocate irq_iommu on node
irq: Add irq_node() primitive
irq: Make sure irq_desc for legacy irq get correct node setting
genirq: Add prototype for handle_nested_irq()
irq: Remove superfluous NULL pointer check in check_irq_resend()
irq: Clean up by removing irqfixup MODULE_PARM_DESC()
genirq: Fix comment describing suspend_device_irqs()
genirq: Remove obsolete defines and typedefs
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (28 commits)
rcu: Move end of special early-boot RCU operation earlier
rcu: Changes from reviews: avoid casts, fix/add warnings, improve comments
rcu: Create rcutree plugins to handle hotplug CPU for multi-level trees
rcu: Remove lockdep annotations from RCU's _notrace() API members
rcu: Add #ifdef to suppress __rcu_offline_cpu() warning in !HOTPLUG_CPU builds
rcu: Add CPU-offline processing for single-node configurations
rcu: Add "notrace" to RCU function headers used by ftrace
rcu: Remove CONFIG_PREEMPT_RCU
rcu: Merge preemptable-RCU functionality into hierarchical RCU
rcu: Simplify rcu_pending()/rcu_check_callbacks() API
rcu: Use debugfs_remove_recursive() simplify code.
rcu: Merge per-RCU-flavor initialization into pre-existing macro
rcu: Fix online/offline indication for rcudata.csv trace file
rcu: Consolidate sparse and lockdep declarations in include/linux/rcupdate.h
rcu: Renamings to increase RCU clarity
rcu: Move private definitions from include/linux/rcutree.h to kernel/rcutree.h
rcu: Expunge lingering references to CONFIG_CLASSIC_RCU, optimize on !SMP
rcu: Delay rcu_barrier() wait until beginning of next CPU-hotunplug operation.
rcu: Fix typo in rcu_irq_exit() comment header
rcu: Make rcupreempt_trace.c look at offline CPUs
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
printk: Fix "printk: Enable the use of more than one CON_BOOT (early console)"
printk: Restore previous console_loglevel when re-enabling logging
printk: Ensure that "console enabled" messages are printed on the console
printk: Enable the use of more than one CON_BOOT (early console)
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (32 commits)
locking, m68k/asm-offsets: Rename signal defines
locking: Inline spinlock code for all locking variants on s390
locking: Simplify spinlock inlining
locking: Allow arch-inlined spinlocks
locking: Move spinlock function bodies to header file
locking, m68k: Calculate thread_info offset with asm offset
locking, m68k/asm-offsets: Rename pt_regs offset defines
locking, sparc: Rename __spin_try_lock() and friends
locking, powerpc: Rename __spin_try_lock() and friends
lockdep: Remove recursion stattistics
lockdep: Simplify lock_stat seqfile code
lockdep: Simplify lockdep_chains seqfile code
lockdep: Simplify lockdep seqfile code
lockdep: Fix missing entries in /proc/lock_chains
lockdep: Fix missing entry in /proc/lock_stat
lockdep: Fix memory usage info of BFS
lockdep: Reintroduce generation count to make BFS faster
lockdep: Deal with many similar locks
lockdep: Introduce lockdep_assert_held()
lockdep: Fix style nits
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-futexes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
futex: Detect mismatched requeue targets
futex: Correct futex_wait_requeue_pi() commentary
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
debug lockups: Improve lockup detection, fix generic arch fallback
debug lockups: Improve lockup detection
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
workqueues: Improve schedule_work() documentation
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* 'writeback' of git://git.kernel.dk/linux-2.6-block:
writeback: check for registered bdi in flusher add and inode dirty
writeback: add name to backing_dev_info
writeback: add some debug inode list counters to bdi stats
writeback: get rid of pdflush completely
writeback: switch to per-bdi threads for flushing data
writeback: move dirty inodes from super_block to backing_dev_info
writeback: get rid of generic_sync_sb_inodes() export
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This enables us to track who does what and print info. Its main use
is catching dirty inodes on the default_backing_dev_info, so we can
fix that up.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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This weird perf trace output:
cc1-9943 [001] 2802.059479616: sched_stat_wait: task: as:9944 wait: 2801938766276 [ns]
Is caused by setting one component field of the delta to zero
a bit too early. Move it to later.
( Note, this does not affect the NEW_FAIR_SLEEPERS interactivity bug,
it's just a reporting bug in essence. )
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nikos Chantziaras <realnc@arcor.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <4AA93D34.8040500@arcor.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Nikos Chantziaras and Jens Axboe reported that turning off
NEW_FAIR_SLEEPERS improves desktop interactivity visibly.
Nikos described his experiences the following way:
" With this setting, I can do "nice -n 19 make -j20" and
still have a very smooth desktop and watch a movie at
the same time. Various other annoyances (like the
"logout/shutdown/restart" dialog of KDE not appearing
at all until the background fade-out effect has finished)
are also gone. So this seems to be the single most
important setting that vastly improves desktop behavior,
at least here. "
Jens described it the following way, referring to a 10-seconds
xmodmap scheduling delay he was trying to debug:
" Then I tried switching NO_NEW_FAIR_SLEEPERS on, and then
I get:
Performance counter stats for 'xmodmap .xmodmap-carl':
9.009137 task-clock-msecs # 0.447 CPUs
18 context-switches # 0.002 M/sec
1 CPU-migrations # 0.000 M/sec
315 page-faults # 0.035 M/sec
0.020167093 seconds time elapsed
Woot! "
So disable it for now. In perf trace output i can see weird
delta timestamps:
cc1-9943 [001] 2802.059479616: sched_stat_wait: task: as:9944 wait: 2801938766276 [ns]
That nsec field is not supposed to be that large. More digging
is needed - but lets turn it off while the real bug is found.
Reported-by: Nikos Chantziaras <realnc@arcor.de>
Tested-by: Nikos Chantziaras <realnc@arcor.de>
Reported-by: Jens Axboe <jens.axboe@oracle.com>
Tested-by: Jens Axboe <jens.axboe@oracle.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <4AA93D34.8040500@arcor.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Removes kthread/workqueue priority boost, they increase worst-case
desktop latencies.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1252486344.28645.18.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Reduce the latency target from 20 msecs to 5 msecs.
Why? Larger latencies increase spread, which is good for scaling,
but bad for worst case latency.
We still have the ilog(nr_cpus) rule to scale up on bigger
server boxes.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1252486344.28645.18.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Set child_runs_first default to off.
It hurts 'optimal' make -j<NR_CPUS> workloads as make jobs
get preempted by child tasks, reducing parallelism.
Note, this patch might make existing races in user
applications more prominent than before - so breakages
might be bisected to this commit.
Child-runs-first is broken on SMP to begin with, and we
already had it off briefly in v2.6.23 so most of the
offenders ought to be fixed. Would be nice not to revert
this commit but fix those apps finally ...
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1252486344.28645.18.camel@marge.simson.net>
[ made the sysctl independent of CONFIG_SCHED_DEBUG, in case
people want to work around broken apps. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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A fork/exec load is usually "pass the baton", so the child
should never be placed behind the parent. With START_DEBIT we
make room for the new task, but with child_runs_first, that
room comes out of the _parent's_ hide. There's nothing to say
that the parent wasn't ahead of min_vruntime at fork() time,
which means that the "baton carrier", who is essentially the
parent in drag, can gain time and increase scheduling latencies
for waiters.
With NEW_FAIR_SLEEPERS + START_DEBIT + child_runs_first
enabled, we essentially pass the sleeper fairness off to the
child, which is fine, but if we don't base placement on the
parent's updated vruntime, we can end up compounding latency
woes if the child itself then does fork/exec. The debit
incurred at fork doesn't hurt the parent who is then going to
sleep and maybe exit, but the child who acquires the error
harms all comers.
This improves latencies of make -j<n> kernel build workloads.
Reported-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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wake_affine() would always fail under low-load situations where
both prev and this were idle, because adding a single task will
always be a significant imbalance, even if there's nothing
around that could balance it.
Deal with this by allowing imbalance when there's nothing you
can do about it.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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select_task_rq_fair() incorrectly skips the wake_affine()
logic, remove this.
When prev_cpu == this_cpu, the code jumps straight to the
wake_idle() logic, this doesn't give the wake_affine() logic
the chance to pin the task to this cpu.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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fix the following 'make includecheck' warning:
kernel/sysctl.c: linux/security.h is included more than once.
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: James Morris <jmorris@namei.org>
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