Track depth in cgroup tree, this is useful for things like
find_matching_se() where you need to get to a common parent of two
sched entities.
Keeping the depth avoids having to calculate it on the spot, which
saves a number of possible cache-misses.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1328936700.2476.17.camel@laptop
Signed-off-by: Ingo Molnar <mingo@kernel.org>
idle_balance() modifies the rq->idle_stamp field, making this information
shared across core.c and fair.c.
As we know if the cpu is going to idle or not with the previous patch, let's
encapsulate the rq->idle_stamp information in core.c by moving it up to the
caller.
The idle_balance() function returns true in case a balancing occured and the
cpu won't be idle, false if no balance happened and the cpu is going idle.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: alex.shi@linaro.org
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389949444-14821-3-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The scheduler main function 'schedule()' checks if there are no more tasks
on the runqueue. Then it checks if a task should be pulled in the current
runqueue in idle_balance() assuming it will go to idle otherwise.
But idle_balance() releases the rq->lock in order to look up the sched
domains and takes the lock again right after. That opens a window where
another cpu may put a task in our runqueue, so we won't go to idle but
we have filled the idle_stamp, thinking we will.
This patch closes the window by checking if the runqueue has been modified
but without pulling a task after taking the lock again, so we won't go to idle
right after in the __schedule() function.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: alex.shi@linaro.org
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389949444-14821-2-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cleanup suggested by Mel Gorman. Now the code contains some more
hints on what statistics go where.
Suggested-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-10-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We track both the node of the memory after a NUMA fault, and the node
of the CPU on which the fault happened. Rename the local variables in
task_numa_fault to make things more explicit.
Suggested-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-9-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The current code in task_numa_placement calculates the difference
between the old and the new value, but also temporarily stores half
of the old value in the per-process variables.
The NUMA balancing code looks at those per-process variables, and
having other tasks temporarily see halved statistics could lead to
unwanted numa migrations. This can be avoided by doing all the math
in local variables.
This change also simplifies the code a little.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-8-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tracing the code that decides the active nodes has made it abundantly clear
that the naive implementation of the faults_from code has issues.
Specifically, the garbage collector in some workloads will access orders
of magnitudes more memory than the threads that do all the active work.
This resulted in the node with the garbage collector being marked the only
active node in the group.
This issue is avoided if we weigh the statistics by CPU use of each task in
the numa group, instead of by how many faults each thread has occurred.
To achieve this, we normalize the number of faults to the fraction of faults
that occurred on each node, and then multiply that fraction by the fraction
of CPU time the task has used since the last time task_numa_placement was
invoked.
This way the nodes in the active node mask will be the ones where the tasks
from the numa group are most actively running, and the influence of eg. the
garbage collector and other do-little threads is properly minimized.
On a 4 node system, using CPU use statistics calculated over a longer interval
results in about 1% fewer page migrations with two 32-warehouse specjbb runs
on a 4 node system, and about 5% fewer page migrations, as well as 1% better
throughput, with two 8-warehouse specjbb runs, as compared with the shorter
term statistics kept by the scheduler.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-7-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Use the active_nodes nodemask to make smarter decisions on NUMA migrations.
In order to maximize performance of workloads that do not fit in one NUMA
node, we want to satisfy the following criteria:
1) keep private memory local to each thread
2) avoid excessive NUMA migration of pages
3) distribute shared memory across the active nodes, to
maximize memory bandwidth available to the workload
This patch accomplishes that by implementing the following policy for
NUMA migrations:
1) always migrate on a private fault
2) never migrate to a node that is not in the set of active nodes
for the numa_group
3) always migrate from a node outside of the set of active nodes,
to a node that is in that set
4) within the set of active nodes in the numa_group, only migrate
from a node with more NUMA page faults, to a node with fewer
NUMA page faults, with a 25% margin to avoid ping-ponging
This results in most pages of a workload ending up on the actively
used nodes, with reduced ping-ponging of pages between those nodes.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-6-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The numa_faults_cpu statistics are used to maintain an active_nodes nodemask
per numa_group. This allows us to be smarter about when to do numa migrations.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-5-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Track which nodes NUMA faults are triggered from, in other words
the CPUs on which the NUMA faults happened. This uses a similar
mechanism to what is used to track the memory involved in numa faults.
The next patches use this to build up a bitmap of which nodes a
workload is actively running on.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-4-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In order to get a more consistent naming scheme, making it clear
which fault statistics track memory locality, and which track
CPU locality, rename the memory fault statistics.
Suggested-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-3-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Excessive migration of pages can hurt the performance of workloads
that span multiple NUMA nodes. However, it turns out that the
p->numa_migrate_deferred knob is a really big hammer, which does
reduce migration rates, but does not actually help performance.
Now that the second stage of the automatic numa balancing code
has stabilized, it is time to replace the simplistic migration
deferral code with something smarter.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Link: http://lkml.kernel.org/r/1390860228-21539-2-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull scheduler fixes from Ingo Molnar:
"A couple of regression fixes mostly hitting virtualized setups, but
also some bare metal systems"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/x86/tsc: Initialize multiplier to 0
sched/clock: Fixup early initialization
sched/preempt/x86: Fix voluntary preempt for x86
Revert "sched: Fix sleep time double accounting in enqueue entity"
This reverts commit 282cf499f0.
With the current implementation, the load average statistics of a sched entity
change according to other activity on the CPU even if this activity is done
between the running window of the sched entity and have no influence on the
running duration of the task.
When a task wakes up on the same CPU, we currently update last_runnable_update
with the return of __synchronize_entity_decay without updating the
runnable_avg_sum and runnable_avg_period accordingly. In fact, we have to sync
the load_contrib of the se with the rq's blocked_load_contrib before removing
it from the latter (with __synchronize_entity_decay) but we must keep
last_runnable_update unchanged for updating runnable_avg_sum/period during the
next update_entity_load_avg.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Cc: pjt@google.com
Cc: alex.shi@linaro.org
Link: http://lkml.kernel.org/r/1390376734-6800-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch adds three tracepoints
o trace_sched_move_numa when a task is moved to a node
o trace_sched_swap_numa when a task is swapped with another task
o trace_sched_stick_numa when a numa-related migration fails
The tracepoints allow the NUMA scheduler activity to be monitored and the
following high-level metrics can be calculated
o NUMA migrated stuck nr trace_sched_stick_numa
o NUMA migrated idle nr trace_sched_move_numa
o NUMA migrated swapped nr trace_sched_swap_numa
o NUMA local swapped trace_sched_swap_numa src_nid == dst_nid (should never happen)
o NUMA remote swapped trace_sched_swap_numa src_nid != dst_nid (should == NUMA migrated swapped)
o NUMA group swapped trace_sched_swap_numa src_ngid == dst_ngid
Maybe a small number of these are acceptable
but a high number would be a major surprise.
It would be even worse if bounces are frequent.
o NUMA avg task migs. Average number of migrations for tasks
o NUMA stddev task mig Self-explanatory
o NUMA max task migs. Maximum number of migrations for a single task
In general the intent of the tracepoints is to help diagnose problems
where automatic NUMA balancing appears to be doing an excessive amount
of useless work.
[akpm@linux-foundation.org: remove semicolon-after-if, repair coding-style]
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>
The test on_null_domain is done twice in the trigger_load_balance function.
Move the test at the begin of the function, so there is only one check.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389008085-9069-9-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The cpu information is stored in the struct rq. Pass the struct rq to
nohz_idle_balance, so all the functions called in run_rebalance_domains have
the same parameters and the 'this_cpu' variable becomes pointless.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
[ Added !SMP build fix. ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389008085-9069-8-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The cpu information is stored in the struct rq and the caller of the
rebalance_domains function pass the cpu to retrieve the struct rq but
it already has the struct rq info. Replace the cpu parameter with the
struct rq.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389008085-9069-7-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The cpu parameter is no longer needed in nohz_balancer_kick, let's remove
the parameter.
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389008085-9069-6-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The 'call_cpu' is never used in the function. Remove it.
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389008085-9069-5-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The on_null_domain() function is getting the cpu to retrieve the struct rq
associated with it.
Pass 'struct rq' directly to the function as the caller already has the info.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389008085-9069-4-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The cpu information is already stored in the struct rq, so no need to pass it
as parameter to the nohz_kick_needed function.
The caller of this function just called idle_cpu() before to fill the
rq->idle_balance field.
Use rq->cpu and rq->idle_balance.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389008085-9069-3-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Thomas Hellstrom bisected a regression where erratic 3D performance is
experienced on virtual machines as measured by glxgears. It identified
commit 58d081b5 ("sched/numa: Avoid overloading CPUs on a preferred NUMA
node") as the problem which had modified the behaviour of effective_load.
Effective load calculates the difference to the system-wide load if a
scheduling entity was moved to another CPU. The task group is not heavier
as a result of the move but overall system load can increase/decrease as a
result of the change. Commit 58d081b5 ("sched/numa: Avoid overloading CPUs
on a preferred NUMA node") changed effective_load to make it suitable for
calculating if a particular NUMA node was compute overloaded. To reduce
the cost of the function, it assumed that a current sched entity weight
of 0 was uninteresting but that is not the case.
wake_affine() uses a weight of 0 for sync wakeups on the grounds that it
is assuming the waking task will sleep and not contribute to load in the
near future. In this case, we still want to calculate the effective load
of the sched entity hierarchy. As effective_load is no longer used by
task_numa_compare since commit fb13c7ee (sched/numa: Use a system-wide
search to find swap/migration candidates), this patch simply restores the
historical behaviour.
Reported-and-tested-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
[ Wrote changelog]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140106113912.GC6178@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The original code is as intended and was meant to scale the difference
between the NUMA_PERIOD_THRESHOLD and local/remote ratio when adjusting
the scan period. The period_slot recalculation can be dropped.
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Rik van Riel <riel@redhat.com>
Link: http://lkml.kernel.org/r/1386833006-6600-4-git-send-email-liwanp@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Use wrapper function task_faults_idx to calculate index in group_faults.
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Rik van Riel <riel@redhat.com>
Link: http://lkml.kernel.org/r/1386833006-6600-3-git-send-email-liwanp@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Use wrapper function task_node to get node which task is on.
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1386833006-6600-2-git-send-email-liwanp@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
commit 887c290e (sched/numa: Decide whether to favour task or group weights
based on swap candidate relationships) drop the check against
sysctl_numa_balancing_settle_count, this patch remove the sysctl.
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Link: http://lkml.kernel.org/r/1386833006-6600-1-git-send-email-liwanp@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Christian suffers from a bad BIOS that wrecks his i5's TSC sync. This
results in him occasionally seeing time going backwards - which
crashes the scheduler ...
Most of our time accounting can actually handle that except the most
common one; the tick time update of sched_fair.
There is a further problem with that code; previously we assumed that
because we get a tick every TICK_NSEC our time delta could never
exceed 32bits and math was simpler.
However, ever since Frederic managed to get NO_HZ_FULL merged; this is
no longer the case since now a task can run for a long time indeed
without getting a tick. It only takes about ~4.2 seconds to overflow
our u32 in nanoseconds.
This means we not only need to better deal with time going backwards;
but also means we need to be able to deal with large deltas.
This patch reworks the entire code and uses mul_u64_u32_shr() as
proposed by Andy a long while ago.
We express our virtual time scale factor in a u32 multiplier and shift
right and the 32bit mul_u64_u32_shr() implementation reduces to a
single 32x32->64 multiply if the time delta is still short (common
case).
For 64bit a 64x64->128 multiply can be used if ARCH_SUPPORTS_INT128.
Reported-and-Tested-by: Christian Engelmayer <cengelma@gmx.at>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: fweisbec@gmail.com
Cc: Paul Turner <pjt@google.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131118172706.GI3866@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Add rq->nr_running to sgs->sum_nr_running directly instead of
assigning it through an intermediate variable nr_running.
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1384508212-25032-1-git-send-email-kamalesh@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
After commit 863bffc808 ("sched/fair: Fix group power_orig
computation"), we can dereference rq->sd before it is set.
Fix this by falling back to power_of() in this case and add a comment
explaining things.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
[ Added comment and tweaked patch. ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: mikey@neuling.org
Link: http://lkml.kernel.org/r/20131113151718.GN21461@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
sa->runnable_avg_sum is of type u32 but after shifting it by NICE_0_SHIFT
bits it is promoted to u64. This of course makes no sense, since the
result will never be more then 32-bit long. Casting sa->runnable_avg_sum
to u64 before it is shifted, fixes this problem.
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1384112521-25177-1-git-send-email-mpn@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Because we're completely unserialized against hotplug its well
possible to try and generate numa stats for an offlined node.
Bail out early (and avoid a /0) in this case. The resulting stats are
all 0 which should result in an undesirable balance target -- not to
mention that actually trying to migrate to an offline CPU will fail.
Reported-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Link: http://lkml.kernel.org/n/tip-orja0qylcvyhxfsuebcyL5sI@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The cpusets code can split up the scheduler's domain tree into
smaller domains. Some of those smaller domains may not cross
NUMA nodes at all, leading to a NULL pointer dereference on the
per-cpu sd_numa pointer.
Tasks cannot be migrated out of their domain, so the patch
also sets p->numa_preferred_nid to whereever they are, to
prevent the migration from being retried over and over again.
Reported-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Link: http://lkml.kernel.org/n/tip-oosqomw0Jput0Jkvoowhrqtu@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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>
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>
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>
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>
__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>
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>
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>
There is a subtle race in migrate_swap, when task P, on CPU A, decides to swap
places with task T, on CPU B.
Task P:
- call migrate_swap
Task T:
- go to sleep, removing itself from the runqueue
Task P:
- double lock the runqueues on CPU A & B
Task T:
- get woken up, place itself on the runqueue of CPU C
Task P:
- see that task T is on a runqueue, and pretend to remove it
from the runqueue on CPU B
Now CPUs B & C both have corrupted scheduler data structures.
This patch fixes it, by holding the pi_lock for both of the tasks
involved in the migrate swap. This prevents task T from waking up,
and placing itself onto another runqueue, until after migrate_swap
has released all locks.
This means that, when migrate_swap checks, task T will be either
on the runqueue where it was originally seen, or not on any
runqueue at all. Migrate_swap deals correctly with of those cases.
Tested-by: Joe Mario <jmario@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: hannes@cmpxchg.org
Cc: aarcange@redhat.com
Cc: srikar@linux.vnet.ibm.com
Cc: tglx@linutronix.de
Cc: hpa@zytor.com
Link: http://lkml.kernel.org/r/20131010181722.GO13848@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
