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commit 7c3f2ab7b844f1a859afbc3d41925e8a0faba5fa upstream.
While discussing the proposed SCHED_DEADLINE patches which in parts
mimic the existing FIFO code it was noticed that the wmb in
rt_set_overloaded() didn't have a matching barrier.
The only site using rt_overloaded() to test the rto_count is
pull_rt_task() and we should issue a matching rmb before then assuming
there's an rto_mask bit set.
Without that smp_rmb() in there we could actually miss seeing the
rto_mask bit.
Also, change to using smp_[wr]mb(), even though this is SMP only code;
memory barriers without smp_ always make me think they're against
hardware of some sort.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: vincent.guittot@linaro.org
Cc: luca.abeni@unitn.it
Cc: bruce.ashfield@windriver.com
Cc: dhaval.giani@gmail.com
Cc: rostedt@goodmis.org
Cc: hgu1972@gmail.com
Cc: oleg@redhat.com
Cc: fweisbec@gmail.com
Cc: darren@dvhart.com
Cc: johan.eker@ericsson.com
Cc: p.faure@akatech.ch
Cc: paulmck@linux.vnet.ibm.com
Cc: raistlin@linux.it
Cc: claudio@evidence.eu.com
Cc: insop.song@gmail.com
Cc: michael@amarulasolutions.com
Cc: liming.wang@windriver.com
Cc: fchecconi@gmail.com
Cc: jkacur@redhat.com
Cc: tommaso.cucinotta@sssup.it
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: harald.gustafsson@ericsson.com
Cc: nicola.manica@disi.unitn.it
Cc: tglx@linutronix.de
Link: http://lkml.kernel.org/r/20131015103507.GF10651@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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commit 5d4cf996cf134e8ddb4f906b8197feb9267c2b77 upstream.
Commit 42eb088e (sched: Avoid NULL dereference on sd_busy) corrected a NULL
dereference on sd_busy but the fix also altered what scheduling domain it
used for the 'sd_llc' percpu variable.
One impact of this is that a task selecting a runqueue may consider
idle CPUs that are not cache siblings as candidates for running.
Tasks are then running on CPUs that are not cache hot.
This was found through bisection where ebizzy threads were not seeing equal
performance and it looked like a scheduling fairness issue. This patch
mitigates but does not completely fix the problem on all machines tested
implying there may be an additional bug or a common root cause. Here are
the average range of performance seen by individual ebizzy threads. It
was tested on top of candidate patches related to x86 TLB range flushing.
4-core machine
3.13.0-rc3 3.13.0-rc3
vanilla fixsd-v3r3
Mean 1 0.00 ( 0.00%) 0.00 ( 0.00%)
Mean 2 0.34 ( 0.00%) 0.10 ( 70.59%)
Mean 3 1.29 ( 0.00%) 0.93 ( 27.91%)
Mean 4 7.08 ( 0.00%) 0.77 ( 89.12%)
Mean 5 193.54 ( 0.00%) 2.14 ( 98.89%)
Mean 6 151.12 ( 0.00%) 2.06 ( 98.64%)
Mean 7 115.38 ( 0.00%) 2.04 ( 98.23%)
Mean 8 108.65 ( 0.00%) 1.92 ( 98.23%)
8-core machine
Mean 1 0.00 ( 0.00%) 0.00 ( 0.00%)
Mean 2 0.40 ( 0.00%) 0.21 ( 47.50%)
Mean 3 23.73 ( 0.00%) 0.89 ( 96.25%)
Mean 4 12.79 ( 0.00%) 1.04 ( 91.87%)
Mean 5 13.08 ( 0.00%) 2.42 ( 81.50%)
Mean 6 23.21 ( 0.00%) 69.46 (-199.27%)
Mean 7 15.85 ( 0.00%) 101.72 (-541.77%)
Mean 8 109.37 ( 0.00%) 19.13 ( 82.51%)
Mean 12 124.84 ( 0.00%) 28.62 ( 77.07%)
Mean 16 113.50 ( 0.00%) 24.16 ( 78.71%)
It's eliminated for one machine and reduced for another.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alex Shi <alex.shi@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: H Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131217092124.GV11295@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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commit 8e8339a3a1069141985daaa2521ba304509ddecd upstream.
Yinghai reported that he saw a /0 in sg_capacity on his EX parts.
Make sure to always initialize power_orig now that we actually use it.
Ideally build_sched_domains() -> init_sched_groups_power() would also
initialize this; but for some yet unexplained reason some setups seem
to miss updates there.
Reported-by: Yinghai Lu <yinghai@kernel.org>
Tested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-l8ng2m9uml6fhibln8wqpom7@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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commit 42eb088ed246a5a817bb45a8b32fe234cf1c0f8b upstream.
Commit 37dc6b50cee9 ("sched: Remove unnecessary iteration over sched
domains to update nr_busy_cpus") forgot to clear 'sd_busy' under some
conditions leading to a possible NULL deref in set_cpu_sd_state_idle().
Reported-by: Anton Blanchard <anton@samba.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131118113701.GF3866@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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commit 37dc6b50cee97954c4e6edcd5b1fa614b76038ee upstream.
nr_busy_cpus parameter is used by nohz_kick_needed() to find out the
number of busy cpus in a sched domain which has SD_SHARE_PKG_RESOURCES
flag set. Therefore instead of updating nr_busy_cpus at every level
of sched domain, since it is irrelevant, we can update this parameter
only at the parent domain of the sd which has this flag set. Introduce
a per-cpu parameter sd_busy which represents this parent domain.
In nohz_kick_needed() we directly query the nr_busy_cpus parameter
associated with the groups of sd_busy.
By associating sd_busy with the highest domain which has
SD_SHARE_PKG_RESOURCES flag set, we cover all lower level domains
which could have this flag set and trigger nohz_idle_balancing if any
of the levels have more than one busy cpu.
sd_busy is irrelevant for asymmetric load balancing. However sd_asym
has been introduced to represent the highest sched domain which has
SD_ASYM_PACKING flag set so that it can be queried directly when
required.
While we are at it, we might as well change the nohz_idle parameter to
be updated at the sd_busy domain level alone and not the base domain
level of a CPU. This will unify the concept of busy cpus at just one
level of sched domain where it is currently used.
Signed-off-by: Preeti U Murthy<preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: svaidy@linux.vnet.ibm.com
Cc: vincent.guittot@linaro.org
Cc: bitbucket@online.de
Cc: benh@kernel.crashing.org
Cc: anton@samba.org
Cc: Morten.Rasmussen@arm.com
Cc: pjt@google.com
Cc: peterz@infradead.org
Cc: mikey@neuling.org
Link: http://lkml.kernel.org/r/20131030031252.23426.4417.stgit@preeti.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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commit 2042abe7977222ef606306faa2dce8fd51e98e65 upstream.
Asymmetric scheduling within a core is a scheduler loadbalancing
feature that is triggered when SD_ASYM_PACKING flag is set. The goal
for the load balancer is to move tasks to lower order idle SMT threads
within a core on a POWER7 system.
In nohz_kick_needed(), we intend to check if our sched domain (core)
is completely busy or we have idle cpu.
The following check for SD_ASYM_PACKING:
(cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu)
already covers the case of checking if the domain has an idle cpu,
because cpumask_first_and() will not yield any set bits if this domain
has no idle cpu.
Hence, nr_busy check against group weight can be removed.
Reported-by: Michael Neuling <michael.neuling@au1.ibm.com>
Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Tested-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: vincent.guittot@linaro.org
Cc: bitbucket@online.de
Cc: benh@kernel.crashing.org
Cc: anton@samba.org
Cc: Morten.Rasmussen@arm.com
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131030031242.23426.13019.stgit@preeti.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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commit 0ac9b1c21874d2490331233b3242085f8151e166 upstream.
Currently, group entity load-weights are initialized to zero. This
admits some races with respect to the first time they are re-weighted in
earlty use. ( Let g[x] denote the se for "g" on cpu "x". )
Suppose that we have root->a and that a enters a throttled state,
immediately followed by a[0]->t1 (the only task running on cpu[0])
blocking:
put_prev_task(group_cfs_rq(a[0]), t1)
put_prev_entity(..., t1)
check_cfs_rq_runtime(group_cfs_rq(a[0]))
throttle_cfs_rq(group_cfs_rq(a[0]))
Then, before unthrottling occurs, let a[0]->b[0]->t2 wake for the first
time:
enqueue_task_fair(rq[0], t2)
enqueue_entity(group_cfs_rq(b[0]), t2)
enqueue_entity_load_avg(group_cfs_rq(b[0]), t2)
account_entity_enqueue(group_cfs_ra(b[0]), t2)
update_cfs_shares(group_cfs_rq(b[0]))
< skipped because b is part of a throttled hierarchy >
enqueue_entity(group_cfs_rq(a[0]), b[0])
...
We now have b[0] enqueued, yet group_cfs_rq(a[0])->load.weight == 0
which violates invariants in several code-paths. Eliminate the
possibility of this by initializing group entity weight.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131016181627.22647.47543.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 927b54fccbf04207ec92f669dce6806848cbec7d upstream.
__start_cfs_bandwidth calls hrtimer_cancel while holding rq->lock,
waiting for the hrtimer to finish. However, if sched_cfs_period_timer
runs for another loop iteration, the hrtimer can attempt to take
rq->lock, resulting in deadlock.
Fix this by ensuring that cfs_b->timer_active is cleared only if the
_latest_ call to do_sched_cfs_period_timer is returning as idle. Then
__start_cfs_bandwidth can just call hrtimer_try_to_cancel and wait for
that to succeed or timer_active == 1.
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131016181622.22647.16643.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit db06e78cc13d70f10877e0557becc88ab3ad2be8 upstream.
hrtimer_expires_remaining does not take internal hrtimer locks and thus
must be guarded against concurrent __hrtimer_start_range_ns (but
returning HRTIMER_RESTART is safe). Use cfs_b->lock to make it safe.
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131016181617.22647.73829.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 1ee14e6c8cddeeb8a490d7b54cd9016e4bb900b4 upstream.
When we transition cfs_bandwidth_used to false, any currently
throttled groups will incorrectly return false from cfs_rq_throttled.
While tg_set_cfs_bandwidth will unthrottle them eventually, currently
running code (including at least dequeue_task_fair and
distribute_cfs_runtime) will cause errors.
Fix this by turning off cfs_bandwidth_used only after unthrottling all
cfs_rqs.
Tested: toggle bandwidth back and forth on a loaded cgroup. Caused
crashes in minutes without the patch, hasn't crashed with it.
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131016181611.22647.80365.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 3c67f474558748b604e247d92b55dfe89654c81d upstream.
Inaccessible VMA should not be trapping NUMA hint faults. Skip them.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 757dfcaa41844595964f1220f1d33182dae49976 upstream.
This patch touches the RT group scheduling case.
Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's
priority, while rt_rq passed to them may be not the top-level rt_rq.
This is wrong, because changing of priority on a child level does not
guarantee that the priority is the highest all over the rq. So, this
leak makes RT balancing unusable.
The short example: the task having the highest priority among all rq's
RT tasks (no one other task has the same priority) are waking on a
throttle rt_rq. The rq's cpupri is set to the task's priority
equivalent, but real rq->rt.highest_prio.curr is less.
The patch below fixes the problem.
Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
CC: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/49231385567953@web4m.yandex.ru
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit f9f9ffc237dd924f048204e8799da74f9ecf40cf upstream.
throttle_cfs_rq() doesn't check to make sure that period_timer is running,
and while update_curr/assign_cfs_runtime does, a concurrently running
period_timer on another cpu could cancel itself between this cpu's
update_curr and throttle_cfs_rq(). If there are no other cfs_rqs running
in the tg to restart the timer, this causes the cfs_rq to be stranded
forever.
Fix this by calling __start_cfs_bandwidth() in throttle if the timer is
inactive.
(Also add some sched_debug lines for cfs_bandwidth.)
Tested: make a run/sleep task in a cgroup, loop switching the cgroup
between 1ms/100ms quota and unlimited, checking for timer_active=0 and
throttled=1 as a failure. With the throttle_cfs_rq() change commented out
this fails, with the full patch it passes.
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131016181632.22647.84174.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Patch a003a2 (sched: Consider runnable load average in move_tasks())
sets all top-level cfs_rqs' h_load to rq->avg.load_avg_contrib, which is
always 0. This mistype leads to all tasks having weight 0 when load
balancing in a cpu-cgroup enabled setup. There obviously should be sum
of weights of all runnable tasks there instead. Fix it.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Reviewed-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1379173186-11944-1-git-send-email-vdavydov@parallels.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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fix_small_imbalance()
In busiest->group_imb case we can come to fix_small_imbalance() with
local->avg_load > busiest->avg_load. This can result in wrong imbalance
fix-up, because there is the following check there where all the
members are unsigned:
if (busiest->avg_load - local->avg_load + scaled_busy_load_per_task >=
(scaled_busy_load_per_task * imbn)) {
env->imbalance = busiest->load_per_task;
return;
}
As a result we can end up constantly bouncing tasks from one cpu to
another if there are pinned tasks.
Fix it by substituting the subtraction with an equivalent addition in
the check.
[ The bug can be caught by running 2*N cpuhogs pinned to two logical cpus
belonging to different cores on an HT-enabled machine with N logical
cpus: just look at se.nr_migrations growth. ]
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/ef167822e5c5b2d96cf5b0e3e4f4bdff3f0414a2.1379252740.git.vdavydov@parallels.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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calculate_imbalance()
In busiest->group_imb case we can come to calculate_imbalance() with
local->avg_load >= busiest->avg_load >= sds->avg_load. This can result
in imbalance overflow, because it is calculated as follows
env->imbalance = min(
max_pull * busiest->group_power,
(sds->avg_load - local->avg_load) * local->group_power) / SCHED_POWER_SCALE;
As a result we can end up constantly bouncing tasks from one cpu to
another if there are pinned tasks.
Fix this by skipping the assignment and assuming imbalance=0 in case
local->avg_load > sds->avg_load.
[ The bug can be caught by running 2*N cpuhogs pinned to two logical cpus
belonging to different cores on an HT-enabled machine with N logical
cpus: just look at se.nr_migrations growth. ]
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/8f596cc6bc0e5e655119dc892c9bfcad26e971f4.1379252740.git.vdavydov@parallels.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar:
"Misc fixes"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched: Fix comment for sched_info_depart
sched/Documentation: Update sched-design-CFS.txt documentation
sched/debug: Take PID namespace into account
sched/fair: Fix small race where child->se.parent,cfs_rq might point to invalid ones
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sched_info_depart seems to be only called from
sched_info_switch(), so only on involuntary task switch.
Fix the comment to match.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Link: http://lkml.kernel.org/r/20130916083036.GA1113@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fix from Ingo Molnar:
"Performance regression fix"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched: Fix load balancing performance regression in should_we_balance()
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Emmanuel reported that /proc/sched_debug didn't report the right PIDs
when using namespaces, cure this.
Reported-by: Emmanuel Deloget <emmanuel.deloget@efixo.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130909110141.GM31370@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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invalid ones
There is a small race between copy_process() and cgroup_attach_task()
where child->se.parent,cfs_rq points to invalid (old) ones.
parent doing fork() | someone moving the parent to another cgroup
-------------------------------+---------------------------------------------
copy_process()
+ dup_task_struct()
-> parent->se is copied to child->se.
se.parent,cfs_rq of them point to old ones.
cgroup_attach_task()
+ cgroup_task_migrate()
-> parent->cgroup is updated.
+ cpu_cgroup_attach()
+ sched_move_task()
+ task_move_group_fair()
+- set_task_rq()
-> se.parent,cfs_rq of parent
are updated.
+ cgroup_fork()
-> parent->cgroup is copied to child->cgroup. (*1)
+ sched_fork()
+ task_fork_fair()
-> se.parent,cfs_rq of child are accessed
while they point to old ones. (*2)
In the worst case, this bug can lead to "use-after-free" and cause a panic,
because it's new cgroup's refcount that is incremented at (*1),
so the old cgroup(and related data) can be freed before (*2).
In fact, a panic caused by this bug was originally caught in RHEL6.4.
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff81051e3e>] sched_slice+0x6e/0xa0
[...]
Call Trace:
[<ffffffff81051f25>] place_entity+0x75/0xa0
[<ffffffff81056a3a>] task_fork_fair+0xaa/0x160
[<ffffffff81063c0b>] sched_fork+0x6b/0x140
[<ffffffff8106c3c2>] copy_process+0x5b2/0x1450
[<ffffffff81063b49>] ? wake_up_new_task+0xd9/0x130
[<ffffffff8106d2f4>] do_fork+0x94/0x460
[<ffffffff81072a9e>] ? sys_wait4+0xae/0x100
[<ffffffff81009598>] sys_clone+0x28/0x30
[<ffffffff8100b393>] stub_clone+0x13/0x20
[<ffffffff8100b072>] ? system_call_fastpath+0x16/0x1b
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/039601ceae06$733d3130$59b79390$@mxp.nes.nec.co.jp
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Commit 23f0d20 ("sched: Factor out code to should_we_balance()")
introduces the should_we_balance() function. This function should
return 1 if this cpu is appropriate for balancing. But the newly
introduced code doesn't do so, it returns 0 instead of 1.
This introduces performance regression, reported by Dave Chinner:
v4 filesystem v5 filesystem
3.11+xfsdev: 220k files/s 225k files/s
3.12-git 180k files/s 185k files/s
3.12-git-revert 245k files/s 247k files/s
You can find more detailed information at:
https://lkml.org/lkml/2013/9/10/1
This patch corrects the return value of should_we_balance()
function as orignally intended.
With this patch, Dave Chinner reports that the regression is gone:
v4 filesystem v5 filesystem
3.11+xfsdev: 220k files/s 225k files/s
3.12-git 180k files/s 185k files/s
3.12-git-revert 245k files/s 247k files/s
3.12-git-fix 249k files/s 248k files/s
Reported-by: Dave Chinner <dchinner@redhat.com>
Tested-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Link: http://lkml.kernel.org/r/20130910065448.GA20368@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull cputime fix from Ingo Molnar:
"This fixes a longer-standing cputime accounting bug that Stanislaw
Gruszka finally managed to track down"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/cputime: Do not scale when utime == 0
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Pull KVM updates from Gleb Natapov:
"The highlights of the release are nested EPT and pv-ticketlocks
support (hypervisor part, guest part, which is most of the code, goes
through tip tree). Apart of that there are many fixes for all arches"
Fix up semantic conflicts as discussed in the pull request thread..
* 'next' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (88 commits)
ARM: KVM: Add newlines to panic strings
ARM: KVM: Work around older compiler bug
ARM: KVM: Simplify tracepoint text
ARM: KVM: Fix kvm_set_pte assignment
ARM: KVM: vgic: Bump VGIC_NR_IRQS to 256
ARM: KVM: Bugfix: vgic_bytemap_get_reg per cpu regs
ARM: KVM: vgic: fix GICD_ICFGRn access
ARM: KVM: vgic: simplify vgic_get_target_reg
KVM: MMU: remove unused parameter
KVM: PPC: Book3S PR: Rework kvmppc_mmu_book3s_64_xlate()
KVM: PPC: Book3S PR: Make instruction fetch fallback work for system calls
KVM: PPC: Book3S PR: Don't corrupt guest state when kernel uses VMX
KVM: x86: update masterclock when kvmclock_offset is calculated (v2)
KVM: PPC: Book3S: Fix compile error in XICS emulation
KVM: PPC: Book3S PR: return appropriate error when allocation fails
arch: powerpc: kvm: add signed type cast for comparation
KVM: x86: add comments where MMIO does not return to the emulator
KVM: vmx: count exits to userspace during invalid guest emulation
KVM: rename __kvm_io_bus_sort_cmp to kvm_io_bus_cmp
kvm: optimize away THP checks in kvm_is_mmio_pfn()
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timers/nohz changes from Ingo Molnar:
"It mostly contains fixes and full dynticks off-case optimizations, by
Frederic Weisbecker"
* 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
nohz: Include local CPU in full dynticks global kick
nohz: Optimize full dynticks's sched hooks with static keys
nohz: Optimize full dynticks state checks with static keys
nohz: Rename a few state variables
vtime: Always debug check snapshot source _before_ updating it
vtime: Always scale generic vtime accounting results
vtime: Optimize full dynticks accounting off case with static keys
vtime: Describe overriden functions in dedicated arch headers
m68k: hardirq_count() only need preempt_mask.h
hardirq: Split preempt count mask definitions
context_tracking: Split low level state headers
vtime: Fix racy cputime delta update
vtime: Remove a few unneeded generic vtime state checks
context_tracking: User/kernel broundary cross trace events
context_tracking: Optimize context switch off case with static keys
context_tracking: Optimize guest APIs off case with static key
context_tracking: Optimize main APIs off case with static key
context_tracking: Ground setup for static key use
context_tracking: Remove full dynticks' hacky dependency on wide context tracking
nohz: Only enable context tracking on full dynticks CPUs
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler changes from Ingo Molnar:
"Various optimizations, cleanups and smaller fixes - no major changes
in scheduler behavior"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/fair: Fix the sd_parent_degenerate() code
sched/fair: Rework and comment the group_imb code
sched/fair: Optimize find_busiest_queue()
sched/fair: Make group power more consistent
sched/fair: Remove duplicate load_per_task computations
sched/fair: Shrink sg_lb_stats and play memset games
sched: Clean-up struct sd_lb_stat
sched: Factor out code to should_we_balance()
sched: Remove one division operation in find_busiest_queue()
sched/cputime: Use this_cpu_add() in task_group_account_field()
cpumask: Fix cpumask leak in partition_sched_domains()
sched/x86: Optimize switch_mm() for multi-threaded workloads
generic-ipi: Kill unnecessary variable - csd_flags
numa: Mark __node_set() as __always_inline
sched/fair: Cleanup: remove duplicate variable declaration
sched/__wake_up_sync_key(): Fix nr_exclusive tasks which lead to WF_SYNC clearing
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf changes from Ingo Molnar:
"As a first remark I'd like to point out that the obsolete '-f'
(--force) option, which has not done anything for several releases,
has been removed from 'perf record' and related utilities. Everyone
please update muscle memory accordingly! :-)
Main changes on the perf kernel side:
- Performance optimizations:
. for trace events, by Steve Rostedt.
. for time values, by Peter Zijlstra
- New hardware support:
. for Intel Silvermont (22nm Atom) CPUs, by Zheng Yan
. for Intel SNB-EP uncore PMUs, by Zheng Yan
- Enhanced hardware support:
. for Intel uncore PMUs: add filter support for QPI boxes, by Zheng Yan
- Core perf events code enhancements and fixes:
. for full-nohz feature handling, by Frederic Weisbecker
. for group events, by Jiri Olsa
. for call chains, by Frederic Weisbecker
. for event stream parsing, by Adrian Hunter
- New ABI details:
. Add attr->mmap2 attribute, by Stephane Eranian
. Add PERF_EVENT_IOC_ID ioctl to return event ID, by Jiri Olsa
. Export u64 time_zero on the mmap header page to allow TSC
calculation, by Adrian Hunter
. Add dummy software event, by Adrian Hunter.
. Add a new PERF_SAMPLE_IDENTIFIER to make samples always
parseable, by Adrian Hunter.
. Make Power7 events available via sysfs, by Runzhen Wang.
- Code cleanups and refactorings:
. for nohz-full, by Frederic Weisbecker
. for group events, by Jiri Olsa
- Documentation updates:
. for perf_event_type, by Peter Zijlstra
Main changes on the perf tooling side (some of these tooling changes
utilize the above kernel side changes):
- Lots of 'perf trace' enhancements:
. Make 'perf trace' command line arguments consistent with
'perf record', by David Ahern.
. Allow specifying syscalls a la strace, by Arnaldo Carvalho de Melo.
. Add --verbose and -o/--output options, by Arnaldo Carvalho de Melo.
. Support ! in -e expressions, to filter a list of syscalls,
by Arnaldo Carvalho de Melo.
. Arg formatting improvements to allow masking arguments in
syscalls such as futex and open, where the some arguments are
ignored and thus should not be printed depending on other args,
by Arnaldo Carvalho de Melo.
. Beautify futex open, openat, open_by_handle_at, lseek and futex
syscalls, by Arnaldo Carvalho de Melo.
. Add option to analyze events in a file versus live, so that
one can do:
[root@zoo ~]# perf record -a -e raw_syscalls:* sleep 1
[ perf record: Woken up 0 times to write data ]
[ perf record: Captured and wrote 25.150 MB perf.data (~1098836 samples) ]
[root@zoo ~]# perf trace -i perf.data -e futex --duration 1
17.799 ( 1.020 ms): 7127 futex(uaddr: 0x7fff3f6c6674, op: 393, val: 1, utime: 0x7fff3f6c6470, ua
113.344 (95.429 ms): 7127 futex(uaddr: 0x7fff3f6c6674, op: 393, val: 1, utime: 0x7fff3f6c6470, uaddr2: 0x7fff3f6c6648, val3: 4294967
133.778 ( 1.042 ms): 18004 futex(uaddr: 0x7fff3f6c6674, op: 393, val: 1, utime: 0x7fff3f6c6470, uaddr2: 0x7fff3f6c6648, val3: 429496
[root@zoo ~]#
By David Ahern.
. Honor target pid / tid options when analyzing a file, by David Ahern.
. Introduce better formatting of syscall arguments, including so
far beautifiers for mmap, madvise, syscall return values,
by Arnaldo Carvalho de Melo.
. Handle HUGEPAGE defines in the mmap beautifier, by David Ahern.
- 'perf report/top' enhancements:
. Do annotation using /proc/kcore and /proc/kallsyms when
available, removing the forced need for a vmlinux file kernel
assembly annotation. This also improves this use case because
vmlinux has just the initial kernel image, not what is actually
in use after various code patchings by things like alternatives.
By Adrian Hunter.
. Add --ignore-callees=<regex> option to collapse undesired parts
of call graphs, by Greg Price.
. Simplify symbol filtering by doing it at machine class level,
by Adrian Hunter.
. Add support for callchains in the gtk UI, by Namhyung Kim.
. Add --objdump option to 'perf top', by Sukadev Bhattiprolu.
- 'perf kvm' enhancements:
. Add option to print only events that exceed a specified time
duration, by David Ahern.
. Improve stack trace printing, by David Ahern.
. Update documentation of the live command, by David Ahern
. Add perf kvm stat live mode that combines aspects of 'perf kvm
stat' record and report, by David Ahern.
. Add option to analyze specific VM in perf kvm stat report, by
David Ahern.
. Do not require /lib/modules/* on a guest, by Jason Wessel.
- 'perf script' enhancements:
. Fix symbol offset computation for some dsos, by David Ahern.
. Fix named threads support, by David Ahern.
. Don't install scripting files files when perl/python support
is disabled, by Arnaldo Carvalho de Melo.
- 'perf test' enhancements:
. Add various improvements and fixes to the "vmlinux matches
kallsyms" 'perf test' entry, related to the /proc/kcore
annotation feature. By Adrian Hunter.
. Add sample parsing test, by Adrian Hunter.
. Add test for reading object code, by Adrian Hunter.
. Add attr record group sampling test, by Jiri Olsa.
. Misc testing infrastructure improvements and other details,
by Jiri Olsa.
- 'perf list' enhancements:
. Skip unsupported hardware events, by Namhyung Kim.
. List pmu events, by Andi Kleen.
- 'perf diff' enhancements:
. Add support for more than two files comparison, by Jiri Olsa.
- 'perf sched' enhancements:
. Various improvements, including removing reliance on some
scheduler tracepoints that provide the same information as the
PERF_RECORD_{FORK,EXIT} events. By David Ahern.
. Remove odd build stall by moving a large struct initialization
from a local variable to a global one, by Namhyung Kim.
- 'perf stat' enhancements:
. Add --initial-delay option to skip measuring for a defined
startup phase, by Andi Kleen.
- Generic perf tooling infrastructure/plumbing changes:
. Tidy up sample parsing validation, by Adrian Hunter.
. Fix up jobserver setup in libtraceevent Makefile.
by Arnaldo Carvalho de Melo.
. Debug improvements, by Adrian Hunter.
. Fix correlation of samples coming after PERF_RECORD_EXIT event,
by David Ahern.
. Improve robustness of the topology parsing code,
by Stephane Eranian.
. Add group leader sampling, that allows just one event in a group
to sample while the other events have just its values read,
by Jiri Olsa.
. Add support for a new modifier "D", which requests that the
event, or group of events, be pinned to the PMU.
By Michael Ellerman.
. Support callchain sorting based on addresses, by Andi Kleen
. Prep work for multi perf data file storage, by Jiri Olsa.
. libtraceevent cleanups, by Namhyung Kim.
And lots and lots of other fixes and code reorganizations that did not
make it into the list, see the shortlog, diffstat and the Git log for
details!"
[ Also merge a leftover from the 3.11 cycle ]
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: Prevent race in unthrottling code
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (237 commits)
perf trace: Tell arg formatters the arg index
perf trace: Add beautifier for open's flags arg
perf trace: Add beautifier for lseek's whence arg
perf tools: Fix symbol offset computation for some dsos
perf list: Skip unsupported events
perf tests: Add 'keep tracking' test
perf tools: Add support for PERF_COUNT_SW_DUMMY
perf: Add a dummy software event to keep tracking
perf trace: Add beautifier for futex 'operation' parm
perf trace: Allow syscall arg formatters to mask args
perf: Convert kmalloc_node(...GFP_ZERO...) to kzalloc_node()
perf: Export struct perf_branch_entry to userspace
perf: Add attr->mmap2 attribute to an event
perf/x86: Add Silvermont (22nm Atom) support
perf/x86: use INTEL_UEVENT_EXTRA_REG to define MSR_OFFCORE_RSP_X
perf trace: Handle missing HUGEPAGE defines
perf trace: Honor target pid / tid options when analyzing a file
perf trace: Add option to analyze events in a file versus live
perf evlist: Add tracepoint lookup by name
perf tests: Add a sample parsing test
...
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scale_stime() silently assumes that stime < rtime, otherwise
when stime == rtime and both values are big enough (operations
on them do not fit in 32 bits), the resulting scaling stime can
be bigger than rtime. In consequence utime = rtime - stime
results in negative value.
User space visible symptoms of the bug are overflowed TIME
values on ps/top, for example:
$ ps aux | grep rcu
root 8 0.0 0.0 0 0 ? S 12:42 0:00 [rcuc/0]
root 9 0.0 0.0 0 0 ? S 12:42 0:00 [rcub/0]
root 10 62422329 0.0 0 0 ? R 12:42 21114581:37 [rcu_preempt]
root 11 0.1 0.0 0 0 ? S 12:42 0:02 [rcuop/0]
root 12 62422329 0.0 0 0 ? S 12:42 21114581:35 [rcuop/1]
root 10 62422329 0.0 0 0 ? R 12:42 21114581:37 [rcu_preempt]
or overflowed utime values read directly from /proc/$PID/stat
Reference:
https://lkml.org/lkml/2013/8/20/259
Reported-and-tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: stable@vger.kernel.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20130904131602.GC2564@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
"A lot of activities on the cgroup front. Most changes aren't visible
to userland at all at this point and are laying foundation for the
planned unified hierarchy.
- The biggest change is decoupling the lifetime management of css
(cgroup_subsys_state) from that of cgroup's. Because controllers
(cpu, memory, block and so on) will need to be dynamically enabled
and disabled, css which is the association point between a cgroup
and a controller may come and go dynamically across the lifetime of
a cgroup. Till now, css's were created when the associated cgroup
was created and stayed till the cgroup got destroyed.
Assumptions around this tight coupling permeated through cgroup
core and controllers. These assumptions are gradually removed,
which consists bulk of patches, and css destruction path is
completely decoupled from cgroup destruction path. Note that
decoupling of creation path is relatively easy on top of these
changes and the patchset is pending for the next window.
- cgroup has its own event mechanism cgroup.event_control, which is
only used by memcg. It is overly complex trying to achieve high
flexibility whose benefits seem dubious at best. Going forward,
new events will simply generate file modified event and the
existing mechanism is being made specific to memcg. This pull
request contains prepatory patches for such change.
- Various fixes and cleanups"
Fixed up conflict in kernel/cgroup.c as per Tejun.
* 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (69 commits)
cgroup: fix cgroup_css() invocation in css_from_id()
cgroup: make cgroup_write_event_control() use css_from_dir() instead of __d_cgrp()
cgroup: make cgroup_event hold onto cgroup_subsys_state instead of cgroup
cgroup: implement CFTYPE_NO_PREFIX
cgroup: make cgroup_css() take cgroup_subsys * instead and allow NULL subsys
cgroup: rename cgroup_css_from_dir() to css_from_dir() and update its syntax
cgroup: fix cgroup_write_event_control()
cgroup: fix subsystem file accesses on the root cgroup
cgroup: change cgroup_from_id() to css_from_id()
cgroup: use css_get() in cgroup_create() to check CSS_ROOT
cpuset: remove an unncessary forward declaration
cgroup: RCU protect each cgroup_subsys_state release
cgroup: move subsys file removal to kill_css()
cgroup: factor out kill_css()
cgroup: decouple cgroup_subsys_state destruction from cgroup destruction
cgroup: replace cgroup->css_kill_cnt with ->nr_css
cgroup: bounce cgroup_subsys_state ref kill confirmation to a work item
cgroup: move cgroup->subsys[] assignment to online_css()
cgroup: reorganize css init / exit paths
cgroup: add __rcu modifier to cgroup->subsys[]
...
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I found that on my WSM box I had a redundant domain:
[ 0.949769] CPU0 attaching sched-domain:
[ 0.953765] domain 0: span 0,12 level SIBLING
[ 0.958335] groups: 0 (cpu_power = 587) 12 (cpu_power = 588)
[ 0.964548] domain 1: span 0-5,12-17 level MC
[ 0.969206] groups: 0,12 (cpu_power = 1175) 1,13 (cpu_power = 1176) 2,14 (cpu_power = 1176) 3,15 (cpu_power = 1176) 4,16 (cpu_power = 1176) 5,17 (cpu_power = 1176)
[ 0.984993] domain 2: span 0-5,12-17 level CPU
[ 0.989822] groups: 0-5,12-17 (cpu_power = 7055)
[ 0.995049] domain 3: span 0-23 level NUMA
[ 0.999620] groups: 0-5,12-17 (cpu_power = 7055) 6-11,18-23 (cpu_power = 7056)
Note how domain 2 has only a single group and spans the same CPUs as
domain 1. We should not keep such domains and do in fact have code to
prune these.
It turns out that the 'new' SD_PREFER_SIBLING flag causes this, it
makes sd_parent_degenerate() fail on the CPU domain. We can easily
fix this by 'ignoring' the SD_PREFER_SIBLING bit and transfering it
to whatever domain ends up covering the span.
With this patch the domains now look like this:
[ 0.950419] CPU0 attaching sched-domain:
[ 0.954454] domain 0: span 0,12 level SIBLING
[ 0.959039] groups: 0 (cpu_power = 587) 12 (cpu_power = 588)
[ 0.965271] domain 1: span 0-5,12-17 level MC
[ 0.969936] groups: 0,12 (cpu_power = 1175) 1,13 (cpu_power = 1176) 2,14 (cpu_power = 1176) 3,15 (cpu_power = 1176) 4,16 (cpu_power = 1176) 5,17 (cpu_power = 1176)
[ 0.985737] domain 2: span 0-23 level NUMA
[ 0.990231] groups: 0-5,12-17 (cpu_power = 7055) 6-11,18-23 (cpu_power = 7056)
Reviewed-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-ys201g4jwukj0h8xcamakxq1@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Rik reported some weirdness due to the group_imb code. As a start to
looking at it, clean it up a little and add a few explanatory
comments.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-caeeqttnla4wrrmhp5uf89gp@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Use for_each_cpu_and() and thereby avoid computing the capacity for
CPUs we know we're not interested in.
Reviewed-by: Paul Turner <pjt@google.com>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-lppceyv6kb3a19g8spmrn20b@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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For easier access, less dereferences and more consistent value, store
the group power in update_sg_lb_stats() and use it thereafter. The
actual value in sched_group::sched_group_power::power can change
throughout the load-balance pass if we're unlucky.
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-739xxqkyvftrhnh9ncudutc7@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Since we already compute (but don't store) the sgs load_per_task value
in update_sg_lb_stats() we might as well store it and not re-compute
it later on.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-ym1vmljiwbzgdnnrwp9azftq@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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We can shrink sg_lb_stats because rq::nr_running is an unsigned int
and cpu numbers are 'int'
Before:
sgs: /* size: 72, cachelines: 2, members: 10 */
sds: /* size: 184, cachelines: 3, members: 7 */
After:
sgs: /* size: 56, cachelines: 1, members: 10 */
sds: /* size: 152, cachelines: 3, members: 7 */
Further we can avoid clearing all of sds since we do a total
clear/assignment of sg_stats in update_sg_lb_stats() with exception of
busiest_stat.avg_load which is referenced in update_sd_pick_busiest().
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-0klzmz9okll8wc0nsudguc9p@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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There is no reason to maintain separate variables for this_group
and busiest_group in sd_lb_stat, except saving some space.
But this structure is always allocated in stack, so this saving
isn't really benificial [peterz: reducing stack space is good; in this
case readability increases enough that I think its still beneficial]
This patch unify these variables, so IMO, readability may be improved.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
[ Rename this to local -- avoids confusion between this_cpu and the C++ this pointer. ]
Reviewed-by: Paul Turner <pjt@google.com>
[ Lots of style edits, a few fixes and a rename. ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1375778203-31343-4-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Now checking whether this cpu is appropriate to balance or not
is embedded into update_sg_lb_stats() and this checking has no direct
relationship to this function. There is not enough reason to place
this checking at update_sg_lb_stats(), except saving one iteration
for sched_group_cpus.
In this patch, I factor out this checking to should_we_balance() function.
And before doing actual work for load_balancing, check whether this cpu is
appropriate to balance via should_we_balance(). If this cpu is not
a candidate for balancing, it quit the work immediately.
With this change, we can save two memset cost and can expect better
compiler optimization.
Below is result of this patch.
* Vanilla *
text data bss dec hex filename
34499 1136 116 35751 8ba7 kernel/sched/fair.o
* Patched *
text data bss dec hex filename
34243 1136 116 35495 8aa7 kernel/sched/fair.o
In addition, rename @balance to @continue_balancing in order to represent
its purpose more clearly.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
[ s/should_balance/continue_balancing/g ]
Reviewed-by: Paul Turner <pjt@google.com>
[ Made style changes and a fix in should_we_balance(). ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1375778203-31343-3-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Remove one division operation in find_busiest_queue() by using
crosswise multiplication:
wl_i / power_i > wl_j / power_j :=
wl_i * power_j > wl_j * power_i
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
[ Expanded the changelog. ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1375778203-31343-2-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Pick up the latest upstream fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Use of a this_cpu() operation reduces the number of instructions used
for accounting (account_user_time()) and frees up some registers. This is in
the scheduler tick hotpath.
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/00000140596dd165-338ff7f5-893b-4fec-b251-aaac5557239e-000000@email.amazonses.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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If doms_new is NULL, partition_sched_domains() will reset ndoms_cur
to 0, and free old sched domains with free_sched_domains(doms_cur, ndoms_cur).
As ndoms_cur is 0, the cpumask will not be freed.
Signed-off-by: Xiaotian Feng <xtfeng@gmail.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1375790802-11857-1-git-send-email-xtfeng@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge Linux 3.11-rc5, to pick up the latest fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge Linux 3.11-rc5, to sync up with the latest upstream fixes since -rc1.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/nohz
Pull nohz improvements from Frederic Weisbecker:
" It mostly contains fixes and full dynticks off-case optimizations. I believe that
distros want to enable this feature so it seems important to optimize the case
where the "nohz_full=" parameter is empty. ie: I'm trying to remove any performance
regression that comes with NO_HZ_FULL=y when the feature is not used.
This patchset improves the current situation a lot (off-case appears to be around 11% faster
with hackbench, although I guess it may vary depending on the configuration but it should be
significantly faster in any case) now there is still some work to do: I can still observe a
remaining loss of 1.6% throughput seen with hackbench compared to CONFIG_NO_HZ_FULL=n. "
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The vtime delta update performed by get_vtime_delta() always check
that the source of the snapshot is valid.
Meanhile the snapshot updaters that rely on get_vtime_delta() also
set the new snapshot origin. But some of them do this right before
the call to get_vtime_delta(), making its debug check useless.
This is easily fixable by moving the snapshot origin update after
the call to get_vtime_delta(). The order doesn't matter there.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
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The cputime accounting in full dynticks can be a subtle
mixup of CPUs using tick based accounting and others using
generic vtime.
As long as the tick can have a share on producing these stats, we
want to scale the result against CFS precise accounting as the tick
can miss some task hiding between the periodic interrupt.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
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If no CPU is in the full dynticks range, we can avoid the full
dynticks cputime accounting through generic vtime along with its
overhead and use the traditional tick based accounting instead.
Let's do this and nope the off case with static keys.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
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get_vtime_delta() must be called under the task vtime_seqlock
with the code that does the cputime accounting flush.
Otherwise the cputime reader can be fooled and run into
a race where it sees the snapshot update but misses the
cputime flush. As a result it can report a cputime that is
way too short.
Fix vtime_account_user() that wasn't complying to that rule.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
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Some generic vtime APIs check if the vtime accounting
is enabled on the local CPU before doing their work.
Some of these are not needed because all their callers already
take care of that. Let's remove the checks on these.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
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Optimize guest entry/exit APIs with static keys. This minimize
the overhead for those who enable CONFIG_NO_HZ_FULL without
always using it. Having no range passed to nohz_full= should
result in the probes overhead to be minimized.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
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