Addressed all the comments from Lukasz and rebased the code to the head
of the linus tree.
There is a need to access the energy model from the userspace. One such
example is the sched_ext schedulers [1]. The userspace part of the
sched_ext schedules could feed the (post-processed) energy-model
information to the BPF part of the scheduler.
Currently, debugfs is the only way to read the energy model from userspace;
however, it lacks proper notification mechanisms when a performance domain
and its associated energy model change.
This patch set introduces a generic netlink for the energy model, as
discussed in [2]. It allows a userspace program to read the performance
domain and its energy model. It notifies the userspace program when a
performance domain is created or deleted or its energy model is updated
through a multicast interface.
Specifically, it supports two commands:
- EM_CMD_GET_PDS: Get the list of information for all performance
domains.
- EM_CMD_GET_PD_TABLE: Get the energy model table of a performance
domain.
Also, it supports three notification events:
- EM_CMD_PD_CREATED: When a performance domain is created.
- EM_CMD_PD_DELETED: When a performance domain is deleted.
- EM_CMD_PD_UPDATED: When the energy model table of a performance domain
is updated.
This can be tested using the tool, tools/net/ynl/pyynl/cli.py, for example,
with the following commands:
$> tools/net/ynl/pyynl/cli.py \
--spec Documentation/netlink/specs/em.yaml \
--do get-pds
$> tools/net/ynl/pyynl/cli.py \
--spec Documentation/netlink/specs/em.yaml \
--do get-pd-table --json '{"pd-id": 0}'
$> tools/net/ynl/pyynl/cli.py \
--spec Documentation/netlink/specs/em.yaml \
--subscribe event --sleep 10
[1] https://lwn.net/Articles/922405/
[2] https://lore.kernel.org/lkml/a82423bc-8c38-4d57-93da-c4f20011cc92@arm.com/
[3] https://lore.kernel.org/lkml/202506140306.tuIoz8rN-lkp@intel.com/#t
ChangeLog v4 -> v5:
- Rebase the code to the head of the linus tree.
- Remove the redundant em_check_capacity_update() call from
em_dev_register_pd_no_update().
- Move patch 3 ("PM: EM: Add an iterator and accessor for the
performance domain") after patch 5 ("PM: EM: Add a skeleton code for
netlink notification").
- Move the declaration of for_each_em_perf_domain() and
em_perf_domain_get_by_id() from energy_model.h to em_netlink.h.
- Fix a typo in patch 7 ("PM: EM: Implement
em_nl_get_pd_table_doit()") and change the variable declaration
order in em_nl_get_pd_table_doit() following the reverse Christmas
tree order.
- Remove the empty skeleton code of em_notify_pd_created/updated() from
patch 8 ("PM: EM: Implement em_notify_pd_deleted()") and introduce
them later where they are actually implemented.
- Change the return type of em_notify_pd_created/updated/deleted()
from int to void, since we don't check it anyway.
ChangeLog v3 -> v4:
- Move patches [3-5] to the first.
- Remove the ending period (".") from all of the patch subjects.
- Rebase the code to v6.17-rc4.
ChangeLog v2 -> v3:
- Properly initialize a return variable in
em_notify_pd_created/updated() at an error path (09/10), reported by
the kernel test robot [3].
- Remove redundant initialization of a return variable in
em_notify_pd_deleted() at an error path (08/10).
ChangeLog v1 -> v2:
- Use YNL to generate boilerplate code. Overhaul the naming conventions
(command, event, notification, attribute) to follow the typical
conventions of other YNL-based netlink implementations.
- Calculate the exact message size instead of using NLMSG_GOODSIZE
when allocating a message (genlmsg_new). This avoids the reallocation
of a message.
- Remove an unnecessary function, em_netlink_exit(), and initialize the
netlink (em_netlink_init) at em_netlink.c without touching energy_model.c.
Changwoo Min (10):
PM: EM: Assign a unique ID when creating a performance domain
PM: EM: Expose the ID of a performance domain via debugfs
PM: EM: Add em.yaml and autogen files
PM: EM: Add a skeleton code for netlink notification
PM: EM: Add an iterator and accessor for the performance domain
PM: EM: Implement em_nl_get_pds_doit()
PM: EM: Implement em_nl_get_pd_table_doit()
PM: EM: Implement em_notify_pd_deleted()
PM: EM: Implement em_notify_pd_created/updated()
PM: EM: Notify an event when the performance domain changes
Documentation/netlink/specs/em.yaml | 113 ++++++++++
MAINTAINERS | 3 +
include/linux/energy_model.h | 4 +
include/uapi/linux/energy_model.h | 62 ++++++
kernel/power/Makefile | 5 +-
kernel/power/em_netlink.c | 311 ++++++++++++++++++++++++++++
kernel/power/em_netlink.h | 39 ++++
kernel/power/em_netlink_autogen.c | 48 +++++
kernel/power/em_netlink_autogen.h | 23 ++
kernel/power/energy_model.c | 83 +++++++-
10 files changed, 689 insertions(+), 2 deletions(-)
create mode 100644 Documentation/netlink/specs/em.yaml
create mode 100644 include/uapi/linux/energy_model.h
create mode 100644 kernel/power/em_netlink.c
create mode 100644 kernel/power/em_netlink.h
create mode 100644 kernel/power/em_netlink_autogen.c
create mode 100644 kernel/power/em_netlink_autogen.h
--
2.51.0