linux.git/kernel/sched/pelt.c, branch v6.8

sched: Make PELT acronym definition searchable

2023-10-13T07:56:30+00:00

The PELT acronym definition can be found right at the top of
kernel/sched/pelt.c (of course), but it cannot be found through use of

grep -r PELT kernel/sched/

Add the acronym "(PELT)" after "Per Entity Load Tracking" at the top of
the source file.

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20231012125824.1260774-1-mathieu.desnoyers@efficios.com

sched/headers: Introduce kernel/sched/build_policy.c and build multiple .c files there

2022-02-23T09:58:33+00:00

Similarly to kernel/sched/build_utility.c, collect all 'scheduling policy' related
source code files into kernel/sched/build_policy.c:

    kernel/sched/idle.c

    kernel/sched/rt.c

    kernel/sched/cpudeadline.c
    kernel/sched/pelt.c

    kernel/sched/cputime.c
    kernel/sched/deadline.c

With the exception of fair.c, which we continue to build as a separate file
for build efficiency and parallelism reasons.

Signed-off-by: Ingo Molnar 
Reviewed-by: Peter Zijlstra

sched: Fix various typos

2021-03-21T23:11:52+00:00

Fix ~42 single-word typos in scheduler code comments.

We have accumulated a few fun ones over the years. :-)

Signed-off-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Mike Galbraith 
Cc: Juri Lelli 
Cc: Vincent Guittot 
Cc: Dietmar Eggemann 
Cc: Steven Rostedt 
Cc: Ben Segall 
Cc: Mel Gorman 
Cc: linux-kernel@vger.kernel.org

sched: Add a tracepoint to track rq->nr_running

2020-07-08T09:39:02+00:00

Add a bare tracepoint trace_sched_update_nr_running_tp which tracks
->nr_running CPU's rq. This is used to accurately trace this data and
provide a visualization of scheduler imbalances in, for example, the
form of a heat map.  The tracepoint is accessed by loading an external
kernel module. An example module (forked from Qais' module and including
the pelt related tracepoints) can be found at:

  https://github.com/auldp/tracepoints-helpers.git

A script to turn the trace-cmd report output into a heatmap plot can be
found at:

  https://github.com/jirvoz/plot-nr-running

The tracepoints are added to add_nr_running() and sub_nr_running() which
are in kernel/sched/sched.h. In order to avoid CREATE_TRACE_POINTS in
the header a wrapper call is used and the trace/events/sched.h include
is moved before sched.h in kernel/sched/core.

Signed-off-by: Phil Auld 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20200629192303.GC120228@lorien.usersys.redhat.com

sched/pelt: Cleanup PELT divider

2020-06-15T12:10:06+00:00

Factorize in a single place the calculation of the divider to be used to
to compute *_avg from *_sum value

Suggested-by: Dietmar Eggemann 
Signed-off-by: Vincent Guittot 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20200612154703.23555-1-vincent.guittot@linaro.org

sched/pelt: Remove redundant cap_scale() definition

2020-06-15T12:10:01+00:00

Besides in PELT cap_scale() is used in the Deadline scheduler class for
scale-invariant bandwidth enforcement.
Remove the cap_scale() definition in kernel/sched/pelt.c and keep the
one in kernel/sched/sched.h.

Signed-off-by: Dietmar Eggemann 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Vincent Guittot 
Link: https://lkml.kernel.org/r/20200603080304.16548-2-dietmar.eggemann@arm.com

sched/pelt: Sync util/runnable_sum with PELT window when propagating

2020-05-19T18:34:14+00:00

update_tg_cfs_*() propagate the impact of the attach/detach of an entity
down into the cfs_rq hierarchy and must keep the sync with the current pelt
window.

Even if we can't sync child cfs_rq and its group se, we can sync the group
se and its parent cfs_rq with current position in the PELT window. In fact,
we must keep them sync in order to stay also synced with others entities
and group entities that are already attached to the cfs_rq.

Signed-off-by: Vincent Guittot 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20200506155301.14288-1-vincent.guittot@linaro.org

sched/pelt: Add support to track thermal pressure

2020-03-06T11:57:17+00:00

Extrapolating on the existing framework to track rt/dl utilization using
pelt signals, add a similar mechanism to track thermal pressure. The
difference here from rt/dl utilization tracking is that, instead of
tracking time spent by a CPU running a RT/DL task through util_avg, the
average thermal pressure is tracked through load_avg. This is because
thermal pressure signal is weighted time "delta" capacity unlike util_avg
which is binary. "delta capacity" here means delta between the actual
capacity of a CPU and the decreased capacity a CPU due to a thermal event.

In order to track average thermal pressure, a new sched_avg variable
avg_thermal is introduced. Function update_thermal_load_avg can be called
to do the periodic bookkeeping (accumulate, decay and average) of the
thermal pressure.

Reviewed-by: Vincent Guittot 
Signed-off-by: Thara Gopinath 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Link: https://lkml.kernel.org/r/20200222005213.3873-2-thara.gopinath@linaro.org

sched/pelt: Add a new runnable average signal

2020-02-24T10:36:36+00:00

Now that runnable_load_avg has been removed, we can replace it by a new
signal that will highlight the runnable pressure on a cfs_rq. This signal
track the waiting time of tasks on rq and can help to better define the
state of rqs.

At now, only util_avg is used to define the state of a rq:
  A rq with more that around 80% of utilization and more than 1 tasks is
  considered as overloaded.

But the util_avg signal of a rq can become temporaly low after that a task
migrated onto another rq which can bias the classification of the rq.

When tasks compete for the same rq, their runnable average signal will be
higher than util_avg as it will include the waiting time and we can use
this signal to better classify cfs_rqs.

The new runnable_avg will track the runnable time of a task which simply
adds the waiting time to the running time. The runnable _avg of cfs_rq
will be the /Sum of se's runnable_avg and the runnable_avg of group entity
will follow the one of the rq similarly to util_avg.

Signed-off-by: Vincent Guittot 
Signed-off-by: Mel Gorman 
Signed-off-by: Ingo Molnar 
Reviewed-by: "Dietmar Eggemann "
Acked-by: Peter Zijlstra 
Cc: Juri Lelli 
Cc: Valentin Schneider 
Cc: Phil Auld 
Cc: Hillf Danton 
Link: https://lore.kernel.org/r/20200224095223.13361-9-mgorman@techsingularity.net

sched/pelt: Remove unused runnable load average

2020-02-24T10:36:36+00:00

Now that runnable_load_avg is no more used, we can remove it to make
space for a new signal.

Signed-off-by: Vincent Guittot 
Signed-off-by: Mel Gorman 
Signed-off-by: Ingo Molnar 
Reviewed-by: "Dietmar Eggemann "
Acked-by: Peter Zijlstra 
Cc: Juri Lelli 
Cc: Valentin Schneider 
Cc: Phil Auld 
Cc: Hillf Danton 
Link: https://lore.kernel.org/r/20200224095223.13361-8-mgorman@techsingularity.net