[PATCH v3 0/6] sched: Add new tracepoints required for EAS testing

From: Qais Yousef
Date: Tue Jun 04 2019 - 07:19:03 EST

Changes in v3:
- Split pelt_rq TP into pelt_cfs, pelt_rq, pelt_dl and pelt_irq
- Replace the fatty preprocessing wrappers with exported helper
functions to access data in unexported structures.
- Remove the now unnecessary headers that were introduced in the
previous versions.
- Postfix the tracepoints with '_tp' to make them standout more in the
code as bare tracepoints with no events associated.
- Updated the example module in [2]
- It demonstrates now how to convert the tracepoints into trace
events that extend the sched events subsystem in tracefs.

Changes in v2:
- Add include guards to the newly added headers
- Rename tracepoints:
sched_load_rq -> pelt_rq
sched_load_se -> pelt_se
- Rename helper functions: s/sched_tp/sched_trace/
- Make sched_trace*() less fat by reducing path size to 20 bytes from
- Fix compilation error when building on UP

The following patches add the bare minimum tracepoints required to perform EAS
testing in Lisa[1].

The new tracepoints are bare in a sense that they don't export any info in
tracefs, hence shouldn't introduce any ABI. The intended way to use them is by
loading a module that will probe the tracepoints and extract the info required
for userspace testing.

It is done in this way because adding new TRACE_EVENTS() is no longer accepted

The tracepoints are focused around tracking PELT signals which is what EAS uses
to make its decision, hence knowing the value of PELT as it changes allows
verifying that EAS is doing the right thing based on synthetic tests that
simulate different scenarios.

Beside EAS, the new tracepoints can help investigate CFS load balancer and CFS
taskgroup handling as they are both based on PELT signals too.

Patch 1 exports autogroup_path function.

Patch 2 adds helper/accessor functions to extract info from unexported data
structures that are passed in the tracepoints. eg: access to sched_avg inside

Patches 3-5 add the new tracepoints.

Patch 6 exports the tracepoints so that out of tree modules can probe the new
tracepoints with least amount of effort - which extends the usefulness of the
tracepoints since creating a module to probe them is the only way to access

An example module that uses these tracepoints is available in [2].

[1] https://github.com/ARM-software/lisa
[2] https://github.com/qais-yousef/tracepoints-helpers/tree/pelt-tps-v3-create-events/sched_tp

Qais Yousef (6):
sched: autogroup: Make autogroup_path() always available
sched: add a new sched_trace_*() helper functions
sched: Add new tracepoints to track pelt at rq level
sched: Add new tracepoint to track pelt at se level
sched: Add sched_overutilized tracepoint
sched: export the newly added tracepoints

include/linux/sched.h | 16 ++++-
include/trace/events/sched.h | 31 ++++++++++
kernel/sched/autogroup.c | 2 -
kernel/sched/core.c | 11 ++++
kernel/sched/fair.c | 117 ++++++++++++++++++++++++++++++++++-
kernel/sched/pelt.c | 11 +++-
6 files changed, 182 insertions(+), 6 deletions(-)