The CFS bandwidth controller limits CPU requests of a task group to
quota during each period. However, parallel workloads might be bursty
so that they get throttled even when their average utilization is under
quota. And they are latency sensitive at the same time so that
throttling them is undesired.

We borrow time now against our future underrun, at the cost of increased
interference against the other system users. All nicely bounded.

Traditional (UP-EDF) bandwidth control is something like:

  (U = \Sum u_i) <= 1

This guaranteeds both that every deadline is met and that the system is
stable. After all, if U were > 1, then for every second of walltime,
we'd have to run more than a second of program time, and obviously miss
our deadline, but the next deadline will be further out still, there is
never time to catch up, unbounded fail.

This work observes that a workload doesn't always executes the full
quota; this enables one to describe u_i as a statistical distribution.

For example, have u_i = {x,e}_i, where x is the p(95) and x+e p(100)
(the traditional WCET). This effectively allows u to be smaller,
increasing the efficiency (we can pack more tasks in the system), but at
the cost of missing deadlines when all the odds line up. However, it
does maintain stability, since every overrun must be paired with an
underrun as long as our x is above the average.

That is, suppose we have 2 tasks, both specify a p(95) value, then we
have a p(95)*p(95) = 90.25% chance both tasks are within their quota and
everything is good. At the same time we have a p(5)p(5) = 0.25% chance
both tasks will exceed their quota at the same time (guaranteed deadline
fail). Somewhere in between there's a threshold where one exceeds and
the other doesn't underrun enough to compensate; this depends on the
specific CDFs.

At the same time, we can say that the worst case deadline miss, will be
\Sum e_i; that is, there is a bounded tardiness (under the assumption
that x+e is indeed WCET).

The benefit of burst is seen when testing with schbench. Default value of
kernel.sched_cfs_bandwidth_slice_us(5ms) and CONFIG_HZ(1000) is used.

	mkdir /sys/fs/cgroup/cpu/test
	echo $$ > /sys/fs/cgroup/cpu/test/cgroup.procs
	echo 100000 > /sys/fs/cgroup/cpu/test/cpu.cfs_quota_us
	echo 100000 > /sys/fs/cgroup/cpu/test/cpu.cfs_burst_us

	./schbench -m 1 -t 3 -r 20 -c 80000 -R 10

The average CPU usage is at 80%. I run this for 10 times, and got long tail
latency for 6 times and got throttled for 8 times.

Tail latencies are shown below, and it wasn't the worst case.

	Latency percentiles (usec)
		50.0000th: 19872
		75.0000th: 21344
		90.0000th: 22176
		95.0000th: 22496
		*99.0000th: 22752
		99.5000th: 22752
		99.9000th: 22752
		min=0, max=22727
	rps: 9.90 p95 (usec) 22496 p99 (usec) 22752 p95/cputime 28.12% p99/cputime 28.44%

The interferenece when using burst is valued by the possibilities for
missing the deadline and the average WCET. Test results showed that when
there many cgroups or CPU is under utilized, the interference is
limited. More details are shown in:
https://lore.kernel.org/lkml/5371BD36-55AE-4F71-B9D7-B86DC32E3D2B@linux.alibaba.com/Co-developed-by: Shanpei Chen <shanpeic@linux.alibaba.com>
Signed-off-by: Shanpei Chen <shanpeic@linux.alibaba.com>
Co-developed-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Huaixin Chang <changhuaixin@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210621092800.23714-2-changhuaixin@linux.alibaba.com

Now cpu.uclamp.min acts as a protection, we need to make sure that the
uclamp request of the task is within the allowed range of the cgroup,
that is it is clamp()'ed correctly by tg->uclamp[UCLAMP_MIN] and
tg->uclamp[UCLAMP_MAX].

As reported by Xuewen [1] we can have some corner cases where there's
inversion between uclamp requested by task (p) and the uclamp values of
the taskgroup it's attached to (tg). Following table demonstrates
2 corner cases:

	           |  p  |  tg  |  effective
	-----------+-----+------+-----------
	CASE 1
	-----------+-----+------+-----------
	uclamp_min | 60% | 0%   |  60%
	-----------+-----+------+-----------
	uclamp_max | 80% | 50%  |  50%
	-----------+-----+------+-----------
	CASE 2
	-----------+-----+------+-----------
	uclamp_min | 0%  | 30%  |  30%
	-----------+-----+------+-----------
	uclamp_max | 20% | 50%  |  20%
	-----------+-----+------+-----------

With this fix we get:

	           |  p  |  tg  |  effective
	-----------+-----+------+-----------
	CASE 1
	-----------+-----+------+-----------
	uclamp_min | 60% | 0%   |  50%
	-----------+-----+------+-----------
	uclamp_max | 80% | 50%  |  50%
	-----------+-----+------+-----------
	CASE 2
	-----------+-----+------+-----------
	uclamp_min | 0%  | 30%  |  30%
	-----------+-----+------+-----------
	uclamp_max | 20% | 50%  |  30%
	-----------+-----+------+-----------

Additionally uclamp_update_active_tasks() must now unconditionally
update both UCLAMP_MIN/MAX because changing the tg's UCLAMP_MAX for
instance could have an impact on the effective UCLAMP_MIN of the tasks.

	           |  p  |  tg  |  effective
	-----------+-----+------+-----------
	old
	-----------+-----+------+-----------
	uclamp_min | 60% | 0%   |  50%
	-----------+-----+------+-----------
	uclamp_max | 80% | 50%  |  50%
	-----------+-----+------+-----------
	*new*
	-----------+-----+------+-----------
	uclamp_min | 60% | 0%   | *60%*
	-----------+-----+------+-----------
	uclamp_max | 80% |*70%* | *70%*
	-----------+-----+------+-----------

[1] https://lore.kernel.org/lkml/CAB8ipk_a6VFNjiEnHRHkUMBKbA+qzPQvhtNjJ_YNzQhqV_o8Zw@mail.gmail.com/

Fixes: 0c18f2ec ("sched/uclamp: Fix wrong implementation of cpu.uclamp.min")
Reported-by: Xuewen Yan <xuewen.yan94@gmail.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210617165155.3774110-1-qais.yousef@arm.com

DL keeps track of the utilization on a per-rq basis with the structure
avg_dl. This utilization is updated during task_tick_dl(),
put_prev_task_dl() and set_next_task_dl(). However, when the current
running task changes its policy, set_next_task_dl() which would usually
take care of updating the utilization when the rq starts running DL
tasks, will not see a such change, leaving the avg_dl structure outdated.
When that very same task will be dequeued later, put_prev_task_dl() will
then update the utilization, based on a wrong last_update_time, leading to
a huge spike in the DL utilization signal.

The signal would eventually recover from this issue after few ms. Even
if no DL tasks are run, avg_dl is also updated in
__update_blocked_others(). But as the CPU capacity depends partly on the
avg_dl, this issue has nonetheless a significant impact on the scheduler.

Fix this issue by ensuring a load update when a running task changes
its policy to DL.

Fixes: 3727e0e1 ("sched/dl: Add dl_rq utilization tracking")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/1624271872-211872-3-git-send-email-vincent.donnefort@arm.com

RT keeps track of the utilization on a per-rq basis with the structure
avg_rt. This utilization is updated during task_tick_rt(),
put_prev_task_rt() and set_next_task_rt(). However, when the current
running task changes its policy, set_next_task_rt() which would usually
take care of updating the utilization when the rq starts running RT tasks,
will not see a such change, leaving the avg_rt structure outdated. When
that very same task will be dequeued later, put_prev_task_rt() will then
update the utilization, based on a wrong last_update_time, leading to a
huge spike in the RT utilization signal.

The signal would eventually recover from this issue after few ms. Even if
no RT tasks are run, avg_rt is also updated in __update_blocked_others().
But as the CPU capacity depends partly on the avg_rt, this issue has
nonetheless a significant impact on the scheduler.

Fix this issue by ensuring a load update when a running task changes
its policy to RT.

Fixes: 371bf427 ("sched/rt: Add rt_rq utilization tracking")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/1624271872-211872-2-git-send-email-vincent.donnefort@arm.com

Change the type and name of task_struct::state. Drop the volatile and
shrink it to an 'unsigned int'. Rename it in order to find all uses
such that we can use READ_ONCE/WRITE_ONCE as appropriate.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20210611082838.550736351@infradead.org

All 6 architectures define TASK_STATE in asm-offsets, but then never
actually use it. Remove the definitions to make sure they never will.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210611082838.472811363@infradead.org

There's an existing helper for setting TASK_RUNNING; must've gotten
lost last time we did this cleanup.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.409696194@infradead.org

Remove yet another few p->state accesses.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.347475156@infradead.org

When ran from the sched-out path (preempt_notifier or perf_event),
p->state is irrelevant to determine preemption. You can get preempted
with !task_is_running() just fine.

The right indicator for preemption is if the task is still on the
runqueue in the sched-out path.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210611082838.285099381@infradead.org

Replace a bunch of 'p->state == TASK_RUNNING' with a new helper:
task_is_running(p).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.222401495@infradead.org

Remove broken task->state references and let wake_up_process() DTRT.

The anti-pattern in these patches breaks the ordering of ->state vs
COND as described in the comment near set_current_state() and can lead
to missed wakeups:

	(OoO load, observes RUNNING)<-.
	for (;;) {                    |
	  t->state = UNINTERRUPTIBLE; |
	  smp_mb();          ,----->  | (observes !COND)
                             |        /
	  if (COND) ---------'       |	COND = 1;
		break;		     `- if (t->state != RUNNING)
					  wake_up_process(t); // not done
	  schedule(); // forever waiting
	}
	t->state = TASK_RUNNING;
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.160855222@infradead.org

This commit in sched/urgent moved the cfs_rq_is_decayed() function:

  a7b359fc: ("sched/fair: Correctly insert cfs_rq's to list on unthrottle")

and this fresh commit in sched/core modified it in the old location:

  9e077b52: ("sched/pelt: Check that *_avg are null when *_sum are")

Merge the two variants.

Conflicts:
	kernel/sched/fair.c
Signed-off-by: Ingo Molnar <mingo@kernel.org>

This is a partial forward-port of Peter Ziljstra's work first posted
at:

   https://lore.kernel.org/lkml/20180530142236.667774973@infradead.org/

Currently select_idle_cpu()'s proportional scheme uses the average idle
time *for when we are idle*, that is temporally challenged.  When a CPU
is not at all idle, we'll happily continue using whatever value we did
see when the CPU goes idle. To fix this, introduce a separate average
idle and age it (the existing value still makes sense for things like
new-idle balancing, which happens when we do go idle).

The overall goal is to not spend more time scanning for idle CPUs than
we're idle for. Otherwise we're inhibiting work. This means that we need to
consider the cost over all the wake-ups between consecutive idle periods.
To track this, the scan cost is subtracted from the estimated average
idle time.

The impact of this patch is related to workloads that have domains that
are fully busy or overloaded. Without the patch, the scan depth may be
too high because a CPU is not reaching idle.

Due to the nature of the patch, this is a regression magnet. It
potentially wins when domains are almost fully busy or overloaded --
at that point searches are likely to fail but idle is not being aged
as CPUs are active so search depth is too large and useless. It will
potentially show regressions when there are idle CPUs and a deep search is
beneficial. This tbench result on a 2-socket broadwell machine partially
illustates the problem

                          5.13.0-rc2             5.13.0-rc2
                             vanilla     sched-avgidle-v1r5
Hmean     1        445.02 (   0.00%)      451.36 *   1.42%*
Hmean     2        830.69 (   0.00%)      846.03 *   1.85%*
Hmean     4       1350.80 (   0.00%)     1505.56 *  11.46%*
Hmean     8       2888.88 (   0.00%)     2586.40 * -10.47%*
Hmean     16      5248.18 (   0.00%)     5305.26 *   1.09%*
Hmean     32      8914.03 (   0.00%)     9191.35 *   3.11%*
Hmean     64     10663.10 (   0.00%)    10192.65 *  -4.41%*
Hmean     128    18043.89 (   0.00%)    18478.92 *   2.41%*
Hmean     256    16530.89 (   0.00%)    17637.16 *   6.69%*
Hmean     320    16451.13 (   0.00%)    17270.97 *   4.98%*

Note that 8 was a regression point where a deeper search would have helped
but it gains for high thread counts when searches are useless. Hackbench
is a more extreme example although not perfect as the tasks idle rapidly

hackbench-process-pipes
                          5.13.0-rc2             5.13.0-rc2
                             vanilla     sched-avgidle-v1r5
Amean     1        0.3950 (   0.00%)      0.3887 (   1.60%)
Amean     4        0.9450 (   0.00%)      0.9677 (  -2.40%)
Amean     7        1.4737 (   0.00%)      1.4890 (  -1.04%)
Amean     12       2.3507 (   0.00%)      2.3360 *   0.62%*
Amean     21       4.0807 (   0.00%)      4.0993 *  -0.46%*
Amean     30       5.6820 (   0.00%)      5.7510 *  -1.21%*
Amean     48       8.7913 (   0.00%)      8.7383 (   0.60%)
Amean     79      14.3880 (   0.00%)     13.9343 *   3.15%*
Amean     110     21.2233 (   0.00%)     19.4263 *   8.47%*
Amean     141     28.2930 (   0.00%)     25.1003 *  11.28%*
Amean     172     34.7570 (   0.00%)     30.7527 *  11.52%*
Amean     203     41.0083 (   0.00%)     36.4267 *  11.17%*
Amean     234     47.7133 (   0.00%)     42.0623 *  11.84%*
Amean     265     53.0353 (   0.00%)     47.7720 *   9.92%*
Amean     296     60.0170 (   0.00%)     53.4273 *  10.98%*
Stddev    1        0.0052 (   0.00%)      0.0025 (  51.57%)
Stddev    4        0.0357 (   0.00%)      0.0370 (  -3.75%)
Stddev    7        0.0190 (   0.00%)      0.0298 ( -56.64%)
Stddev    12       0.0064 (   0.00%)      0.0095 ( -48.38%)
Stddev    21       0.0065 (   0.00%)      0.0097 ( -49.28%)
Stddev    30       0.0185 (   0.00%)      0.0295 ( -59.54%)
Stddev    48       0.0559 (   0.00%)      0.0168 (  69.92%)
Stddev    79       0.1559 (   0.00%)      0.0278 (  82.17%)
Stddev    110      1.1728 (   0.00%)      0.0532 (  95.47%)
Stddev    141      0.7867 (   0.00%)      0.0968 (  87.69%)
Stddev    172      1.0255 (   0.00%)      0.0420 (  95.91%)
Stddev    203      0.8106 (   0.00%)      0.1384 (  82.92%)
Stddev    234      1.1949 (   0.00%)      0.1328 (  88.89%)
Stddev    265      0.9231 (   0.00%)      0.0820 (  91.11%)
Stddev    296      1.0456 (   0.00%)      0.1327 (  87.31%)

Again, higher thread counts benefit and the standard deviation
shows that results are also a lot more stable when the idle
time is aged.

The patch potentially matters when a socket was multiple LLCs as the
maximum search depth is lower. However, some of the test results were
suspiciously good (e.g. specjbb2005 gaining 50% on a Zen1 machine) and
other results were not dramatically different to other mcahines.

Given the nature of the patch, Peter's full series is not being forward
ported as each part should stand on its own. Preferably they would be
merged at different times to reduce the risk of false bisections.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210615111611.GH30378@techsingularity.net

Energy Aware Scheduling (EAS) needs to predict the decisions made by
SchedUtil. The map_util_freq() exists to do that.

There are corner cases where the max allowed frequency might be reduced
(due to thermal). SchedUtil as a CPUFreq governor, is aware of that
but EAS is not. This patch aims to address it.

SchedUtil stores the maximum allowed frequency in
'sugov_policy::next_freq' field. EAS has to predict that value, which is
the real used frequency. That value is made after a call to
cpufreq_driver_resolve_freq() which clamps to the CPUFreq policy limits.
In the existing code EAS is not able to predict that real frequency.
This leads to energy estimation errors.

To avoid wrong energy estimation in EAS (due to frequency miss prediction)
make sure that the step which calculates Performance Domain frequency,
is also aware of the allowed CPU capacity.

Furthermore, modify map_util_freq() to not extend the frequency value.
Instead, use map_util_perf() to extend the util value in both places:
SchedUtil and EAS, but for EAS clamp it to max allowed CPU capacity.
In the end, we achieve the same desirable behavior for both subsystems
and alignment in regards to the real CPU frequency.
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> (For the schedutil part)
Link: https://lore.kernel.org/r/20210614191238.23224-1-lukasz.luba@arm.com

Energy Aware Scheduling (EAS) needs to be able to predict the frequency
requests made by the SchedUtil governor to properly estimate energy used
in the future. It has to take into account CPUs utilization and forecast
Performance Domain (PD) frequency. There is a corner case when the max
allowed frequency might be reduced due to thermal. SchedUtil is aware of
that reduced frequency, so it should be taken into account also in EAS
estimations.

SchedUtil, as a CPUFreq governor, knows the maximum allowed frequency of
a CPU, thanks to cpufreq_driver_resolve_freq() and internal clamping
to 'policy::max'. SchedUtil is responsible to respect that upper limit
while setting the frequency through CPUFreq drivers. This effective
frequency is stored internally in 'sugov_policy::next_freq' and EAS has
to predict that value.

In the existing code the raw value of arch_scale_cpu_capacity() is used
for clamping the returned CPU utilization from effective_cpu_util().
This patch fixes issue with too big single CPU utilization, by introducing
clamping to the allowed CPU capacity. The allowed CPU capacity is a CPU
capacity reduced by thermal pressure raw value.

Thanks to knowledge about allowed CPU capacity, we don't get too big value
for a single CPU utilization, which is then added to the util sum. The
util sum is used as a source of information for estimating whole PD energy.
To avoid wrong energy estimation in EAS (due to capped frequency), make
sure that the calculation of util sum is aware of allowed CPU capacity.

This thermal pressure might be visible in scenarios where the CPUs are not
heavily loaded, but some other component (like GPU) drastically reduced
available power budget and increased the SoC temperature. Thus, we still
use EAS for task placement and CPUs are not over-utilized.
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20210614191128.22735-1-lukasz.luba@arm.com

The thermal pressure signal gives information to the scheduler about
reduced CPU capacity due to thermal. It is based on a value stored in
a per-cpu 'thermal_pressure' variable. The online CPUs will get the
new value there, while the offline won't. Unfortunately, when the CPU
is back online, the value read from per-cpu variable might be wrong
(stale data).  This might affect the scheduler decisions, since it
sees the CPU capacity differently than what is actually available.

Fix it by making sure that all online+offline CPUs would get the
proper value in their per-cpu variable when thermal framework sets
capping.

Fixes: f12e4f66 ("thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping")
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/20210614191030.22241-1-lukasz.luba@arm.com

In case the _avg delta is 0 there is no need to update se's _avg
(level n) nor cfs_rq's _avg (level n-1). These values stay the same.

Since cfs_rq's _avg isn't changed, i.e. no load is propagated down,
cfs_rq's _sum should stay the same as well.

So bail out after se's _sum has been updated.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210601083616.804229-1-dietmar.eggemann@arm.com

Check that we never break the rule that pelt's avg values are null if
pelt's sum are.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Odin Ugedal <odin@uged.al>
Link: https://lore.kernel.org/r/20210601155328.19487-1-vincent.guittot@linaro.org

Fix an issue where fairness is decreased since cfs_rq's can end up not
being decayed properly. For two sibling control groups with the same
priority, this can often lead to a load ratio of 99/1 (!!).

This happens because when a cfs_rq is throttled, all the descendant
cfs_rq's will be removed from the leaf list. When they initial cfs_rq
is unthrottled, it will currently only re add descendant cfs_rq's if
they have one or more entities enqueued. This is not a perfect
heuristic.

Instead, we insert all cfs_rq's that contain one or more enqueued
entities, or it its load is not completely decayed.

Can often lead to situations like this for equally weighted control
groups:

  $ ps u -C stress
  USER         PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
  root       10009 88.8  0.0   3676   100 pts/1    R+   11:04   0:13 stress --cpu 1
  root       10023  3.0  0.0   3676   104 pts/1    R+   11:04   0:00 stress --cpu 1

Fixes: 31bc6aea ("sched/fair: Optimize update_blocked_averages()")
[vingo: !SMP build fix]
Signed-off-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210612112815.61678-1-odin@uged.al

Merge tag 'perf-tools-fixes-for-v5.13-2021-06-13' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux

Pull perf tools fixes from Arnaldo Carvalho de Melo:

 - Correct buffer copying when peeking events

 - Sync cpufeatures/disabled-features.h header with the kernel sources

* tag 'perf-tools-fixes-for-v5.13-2021-06-13' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux:
  tools headers cpufeatures: Sync with the kernel sources
  perf session: Correct buffer copying when peeking events

Pull NFS client bugfixes from Trond Myklebust:
 "Highlights include:

  Stable fixes:

   - Fix use-after-free in nfs4_init_client()

  Bugfixes:

   - Fix deadlock between nfs4_evict_inode() and nfs4_opendata_get_inode()

   - Fix second deadlock in nfs4_evict_inode()

   - nfs4_proc_set_acl should not change the value of NFS_CAP_UIDGID_NOMAP

   - Fix setting of the NFS_CAP_SECURITY_LABEL capability"

* tag 'nfs-for-5.13-3' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  NFSv4: Fix second deadlock in nfs4_evict_inode()
  NFSv4: Fix deadlock between nfs4_evict_inode() and nfs4_opendata_get_inode()
  NFS: FMODE_READ and friends are C macros, not enum types
  NFS: Fix a potential NULL dereference in nfs_get_client()
  NFS: Fix use-after-free in nfs4_init_client()
  NFS: Ensure the NFS_CAP_SECURITY_LABEL capability is set when appropriate
  NFSv4: nfs4_proc_set_acl needs to restore NFS_CAP_UIDGID_NOMAP on error.

Pull SCSI fixes from James Bottomley:
 "Four reasonably small fixes to the core for scsi host allocation
  failure paths.

  The root problem is that we're not freeing the memory allocated by
  dev_set_name(), which involves a rejig of may of the free on error
  paths to do put_device() instead of kfree which, in turn, has several
  other knock on ramifications and inspection turned up a few other
  lurking bugs"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: core: Only put parent device if host state differs from SHOST_CREATED
  scsi: core: Put .shost_dev in failure path if host state changes to RUNNING
  scsi: core: Fix failure handling of scsi_add_host_with_dma()
  scsi: core: Fix error handling of scsi_host_alloc()

Pull RISC-V fixes from Palmer Dabbelt:

 - A pair of XIP fixes: one to fix alternatives, and one to turn off the
   rest of the features that require code modification

 - A fix to a type that was causing some alternatives to break

 - A build fix for BUILTIN_DTB

* tag 'riscv-for-linus-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: Fix BUILTIN_DTB for sifive and microchip soc
  riscv: alternative: fix typo in macro name
  riscv: code patching only works on !XIP_KERNEL
  riscv: xip: support runtime trap patching

0day robot reported a 9.2% regression for will-it-scale mmap1 test
case[1], caused by commit 57efa1fe ("mm/gup: prevent gup_fast from
racing with COW during fork").

Further debug shows the regression is due to that commit changes the
offset of hot fields 'mmap_lock' inside structure 'mm_struct', thus some
cache alignment changes.

From the perf data, the contention for 'mmap_lock' is very severe and
takes around 95% cpu cycles, and it is a rw_semaphore

        struct rw_semaphore {
                atomic_long_t count;	/* 8 bytes */
                atomic_long_t owner;	/* 8 bytes */
                struct optimistic_spin_queue osq; /* spinner MCS lock */
                ...

Before commit 57efa1fe adds the 'write_protect_seq', it happens to
have a very optimal cache alignment layout, as Linus explained:

 "and before the addition of the 'write_protect_seq' field, the
  mmap_sem was at offset 120 in 'struct mm_struct'.

  Which meant that count and owner were in two different cachelines,
  and then when you have contention and spend time in
  rwsem_down_write_slowpath(), this is probably *exactly* the kind
  of layout you want.

  Because first the rwsem_write_trylock() will do a cmpxchg on the
  first cacheline (for the optimistic fast-path), and then in the
  case of contention, rwsem_down_write_slowpath() will just access
  the second cacheline.

  Which is probably just optimal for a load that spends a lot of
  time contended - new waiters touch that first cacheline, and then
  they queue themselves up on the second cacheline."

After the commit, the rw_semaphore is at offset 128, which means the
'count' and 'owner' fields are now in the same cacheline, and causes
more cache bouncing.

Currently there are 3 "#ifdef CONFIG_XXX" before 'mmap_lock' which will
affect its offset:

  CONFIG_MMU
  CONFIG_MEMBARRIER
  CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES

The layout above is on 64 bits system with 0day's default kernel config
(similar to RHEL-8.3's config), in which all these 3 options are 'y'.
And the layout can vary with different kernel configs.

Relayouting a structure is usually a double-edged sword, as sometimes it
can helps one case, but hurt other cases.  For this case, one solution
is, as the newly added 'write_protect_seq' is a 4 bytes long seqcount_t
(when CONFIG_DEBUG_LOCK_ALLOC=n), placing it into an existing 4 bytes
hole in 'mm_struct' will not change other fields' alignment, while
restoring the regression.

Link: https://lore.kernel.org/lkml/20210525031636.GB7744@xsang-OptiPlex-9020/ [1]
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull USB fixes from Greg KH:
 "Here are a number of tiny USB fixes for 5.13-rc6.

  There are more than I would normally like, but there's been a bunch of
  people banging on the gadget and dwc3 and typec code recently for I
  think an Android release, which has resulted in a number of small
  fixes. It's nice to see companies send fixes upstream for this type of
  work, a notable change from years ago.

  Anyway, fixes in here are:

   - usb-serial device id updates

   - usb-serial cp210x driver fixes for broken firmware versions

   - typec fixes for crazy charging devices and other reported problems

   - dwc3 fixes for reported problems found

   - gadget fixes for reported problems

   - tiny xhci fixes

   - other small fixes for reported issues.

   - revert of a problem fix found by linux-next testing

  All of these have passed 0-day and linux-next testing with no reported
  problems (the revert for the found linux-next build problem included)"

* tag 'usb-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (44 commits)
  Revert "usb: gadget: fsl: Re-enable driver for ARM SoCs"
  usb: typec: mux: Fix copy-paste mistake in typec_mux_match
  usb: typec: ucsi: Clear PPM capability data in ucsi_init() error path
  usb: gadget: fsl: Re-enable driver for ARM SoCs
  usb: typec: wcove: Use LE to CPU conversion when accessing msg->header
  USB: serial: cp210x: fix CP2102N-A01 modem control
  USB: serial: cp210x: fix alternate function for CP2102N QFN20
  usb: misc: brcmstb-usb-pinmap: check return value after calling platform_get_resource()
  usb: dwc3: ep0: fix NULL pointer exception
  usb: gadget: eem: fix wrong eem header operation
  usb: typec: intel_pmc_mux: Put ACPI device using acpi_dev_put()
  usb: typec: intel_pmc_mux: Add missed error check for devm_ioremap_resource()
  usb: typec: intel_pmc_mux: Put fwnode in error case during ->probe()
  usb: typec: tcpm: Do not finish VDM AMS for retrying Responses
  usb: fix various gadget panics on 10gbps cabling
  usb: fix various gadgets null ptr deref on 10gbps cabling.
  usb: pci-quirks: disable D3cold on xhci suspend for s2idle on AMD Renoir
  usb: f_ncm: only first packet of aggregate needs to start timer
  USB: f_ncm: ncm_bitrate (speed) is unsigned
  MAINTAINERS: usb: add entry for isp1760
  ...

Pull serial driver fix from Greg KH:
 "A single 8250_exar serial driver fix for a reported problem with a
  change that happened in 5.13-rc1.

  It has been in linux-next with no reported problems"

* tag 'tty-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  serial: 8250_exar: Avoid NULL pointer dereference at ->exit()

Pull staging driver fixes from Greg KH:
 "Two tiny staging driver fixes:

   - ralink-gdma driver authorship information fixed up

   - rtl8723bs driver fix for reported regression

  Both have been in linux-next for a while with no reported problems"

* tag 'staging-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  staging: ralink-gdma: Remove incorrect author information
  staging: rtl8723bs: Fix uninitialized variables

Merge tag 'driver-core-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core fix from Greg KH:
 "A single debugfs fix for 5.13-rc6, fixing a bug in
  debugfs_read_file_str() that showed up in 5.13-rc1.

  It has been in linux-next for a full week with no
  reported problems"

* tag 'driver-core-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  debugfs: Fix debugfs_read_file_str()

Pull char/misc driver fixes from Greg KH:
 "Here are some small misc driver fixes for 5.13-rc6 that fix some
  reported problems:

   - Tiny phy driver fixes for reported issues

   - rtsx regression for when the device suspended

   - mhi driver fix for a use-after-free

  All of these have been in linux-next for a few days with no reported
  issues"

* tag 'char-misc-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  misc: rtsx: separate aspm mode into MODE_REG and MODE_CFG
  bus: mhi: pci-generic: Fix hibernation
  bus: mhi: pci_generic: Fix possible use-after-free in mhi_pci_remove()
  bus: mhi: pci_generic: T99W175: update channel name from AT to DUN
  phy: Sparx5 Eth SerDes: check return value after calling platform_get_resource()
  phy: ralink: phy-mt7621-pci: drop 'of_match_ptr' to fix -Wunused-const-variable
  phy: ti: Fix an error code in wiz_probe()
  phy: phy-mtk-tphy: Fix some resource leaks in mtk_phy_init()
  phy: cadence: Sierra: Fix error return code in cdns_sierra_phy_probe()
  phy: usb: Fix misuse of IS_ENABLED

Pull pin control fixes from Linus Walleij:

 - Fix some documentation warnings for Allwinner

 - Fix duplicated GPIO groups on Qualcomm SDX55

 - Fix a double enablement bug in the Ralink driver

 - Fix the Qualcomm SC8180x Kconfig so the driver can be selected.

* tag 'pinctrl-v5.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
  pinctrl: qcom: Make it possible to select SC8180x TLMM
  pinctrl: ralink: rt2880: avoid to error in calls is pin is already enabled
  pinctrl: qcom: Fix duplication in gpio_groups
  pinctrl: aspeed: Fix minor documentation error

Pull block fixes from Jens Axboe:
 "A few fixes that should go into 5.13:

   - Fix a regression deadlock introduced in this release between open
     and remove of a bdev (Christoph)

   - Fix an async_xor md regression in this release (Xiao)

   - Fix bcache oversized read issue (Coly)"

* tag 'block-5.13-2021-06-12' of git://git.kernel.dk/linux-block:
  block: loop: fix deadlock between open and remove
  async_xor: check src_offs is not NULL before updating it
  bcache: avoid oversized read request in cache missing code path
  bcache: remove bcache device self-defined readahead

Pull io_uring fixes from Jens Axboe:
 "Just an API change for the registration changes that went into this
  release. Better to get it sorted out now than before it's too late"

* tag 'io_uring-5.13-2021-06-12' of git://git.kernel.dk/linux-block:
  io_uring: add feature flag for rsrc tags
  io_uring: change registration/upd/rsrc tagging ABI

Pull scheduler fixes from Ingo Molnar:
 "Misc fixes:

   - Fix performance regression caused by lack of intended batching of
     RCU callbacks by over-eager NOHZ-full code.

   - Fix cgroups related corruption of load_avg and load_sum metrics.

   - Three fixes to fix blocked load, util_sum/runnable_sum and util_est
     tracking bugs"

* tag 'sched-urgent-2021-06-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Fix util_est UTIL_AVG_UNCHANGED handling
  sched/pelt: Ensure that *_sum is always synced with *_avg
  tick/nohz: Only check for RCU deferred wakeup on user/guest entry when needed
  sched/fair: Make sure to update tg contrib for blocked load
  sched/fair: Keep load_avg and load_sum synced

Pull perf fixes from Ingo Molnar:
 "Misc fixes:

   - Fix the NMI watchdog on ancient Intel CPUs

   - Remove a misguided, NMI-unsafe KASAN callback from the NMI-safe
     irq_work path used by perf.

   - Fix uncore events on Ice Lake servers.

   - Someone booted maxcpus=1 on an SNB-EP, and the uncore driver
     emitted warnings and was probably buggy. Fix it.

   - KCSAN found a genuine data race in the core perf code. Somewhat
     ironically the bug was introduced through a recent race fix. :-/
     In our defense, the new race window was much more narrow. Fix it"

* tag 'perf-urgent-2021-06-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/nmi_watchdog: Fix old-style NMI watchdog regression on old Intel CPUs
  irq_work: Make irq_work_queue() NMI-safe again
  perf/x86/intel/uncore: Fix M2M event umask for Ice Lake server
  perf/x86/intel/uncore: Fix a kernel WARNING triggered by maxcpus=1
  perf: Fix data race between pin_count increment/decrement

Pull objtool fixes from Ingo Molnar:
 "Two objtool fixes:

   - fix a bug that corrupts the code by mistakenly rewriting
     conditional jumps

   - fix another bug generating an incorrect ELF symbol table
     during retpoline rewriting"

* tag 'objtool-urgent-2021-06-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Only rewrite unconditional retpoline thunk calls
  objtool: Fix .symtab_shndx handling for elf_create_undef_symbol()

Fix BUILTIN_DTB config which resulted in a dtb that was actually not
built into the Linux image: in the same manner as Canaan soc does,
create an object file from the dtb file that will get linked into the
Linux image.
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

Pull tracing fixes from Steven Rostedt:

 - Fix the length check in the temp buffer filter

 - Fix build failure in bootconfig tools for "fallthrough" macro

 - Fix error return of bootconfig apply_xbc() routine

* tag 'trace-v5.13-rc5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Correct the length check which causes memory corruption
  ftrace: Do not blindly read the ip address in ftrace_bug()
  tools/bootconfig: Fix a build error accroding to undefined fallthrough
  tools/bootconfig: Fix error return code in apply_xbc()

Pull clang LTO fix from Kees Cook:
 "Clang 13 fixed some IR behavior for LTO, but this broke work-arounds
  used in the kernel.

  Handle changes to needed LTO flags in Clang 13 (Tor Vic)"

* tag 'clang-features-v5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  x86, lto: Pass -stack-alignment only on LLD < 13.0.0

Pull gpio fix from Bartosz Golaszewski:
 "Fix a shift-out-of-bounds error in gpio-wcd934x"

* tag 'gpio-fixes-for-v5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux:
  gpio: wcd934x: Fix shift-out-of-bounds error