| From: |
| Samuel Wu <wusamuel-AT-google.com> |
| To: |
| "Rafael J. Wysocki" <rafael-AT-kernel.org>, Len Brown <lenb-AT-kernel.org>, Pavel Machek <pavel-AT-kernel.org>, Greg Kroah-Hartman <gregkh-AT-linuxfoundation.org>, Danilo Krummrich <dakr-AT-kernel.org>, Alexei Starovoitov <ast-AT-kernel.org>, Daniel Borkmann <daniel-AT-iogearbox.net>, Andrii Nakryiko <andrii-AT-kernel.org>, Martin KaFai Lau <martin.lau-AT-linux.dev>, Eduard Zingerman <eddyz87-AT-gmail.com>, Song Liu <song-AT-kernel.org>, Yonghong Song <yonghong.song-AT-linux.dev>, John Fastabend <john.fastabend-AT-gmail.com>, KP Singh <kpsingh-AT-kernel.org>, Stanislav Fomichev <sdf-AT-fomichev.me>, Hao Luo <haoluo-AT-google.com>, Jiri Olsa <jolsa-AT-kernel.org>, Shuah Khan <shuah-AT-kernel.org> |
| Subject: |
| [PATCH v2 0/2] Support BPF traversal of wakeup sources |
| Date: |
| Thu, 26 Mar 2026 04:25:18 -0700 |
| Message-ID: |
| <20260326112521.2827500-1-wusamuel@google.com> |
| Cc: |
| memxor-AT-gmail.com, Samuel Wu <wusamuel-AT-google.com>, kernel-team-AT-android.com, linux-kernel-AT-vger.kernel.org, linux-pm-AT-vger.kernel.org, driver-core-AT-lists.linux.dev, bpf-AT-vger.kernel.org, linux-kselftest-AT-vger.kernel.org |
| Archive-link: |
| Article |
This patchset adds requisite kfuncs for BPF programs to safely traverse
wakeup_sources, and puts a config flag around the sysfs interface.
Currently, a traversal of wakeup sources require going through
/sys/class/wakeup/* or /d/wakeup_sources/*. The repeated syscalls to query
sysfs is inefficient, as there can be hundreds of wakeup_sources, with each
wakeup source also having multiple attributes. debugfs is unstable and
insecure.
Adding kfuncs to lock/unlock wakeup sources allows BPF program to safely
traverse the wakeup sources list. The head address of wakeup_sources can
safely be resolved through BPF helper functions or variable attributes.
On a quiescent Pixel 6 traversing 150 wakeup_sources, I am seeing ~34x
speedup (sampled 75 times in table below). For a device under load, the
speedup is greater.
+-------+----+----------+----------+
| | n | AVG (ms) | STD (ms) |
+-------+----+----------+----------+
| sysfs | 75 | 44.9 | 12.6 |
+-------+----+----------+----------+
| BPF | 75 | 1.3 | 0.7 |
+-------+----+----------+----------+
The initial attempts for BPF traversal of wakeup_sources was with BPF
iterators [1]. However, BPF already allows for traversing of a simple list
with bpf_for(), and this current patchset has the added benefit of being
~2-3x more performant than BPF iterators.
[1]: https://lore.kernel.org/all/20260225210820.177674-1-wusam...
Changes in v2:
- Dropped CONFIG_PM_WAKEUP_STATS_SYSFS patch for future patchset
- Added declarations for kfuncs to .h to fix sparse and checkpatch warnings
- Added kfunc to get address of wakeup_source's head
- Added example bpf prog selftest for traversal of wakeup sources per Kumar
- Added *_fail.c selftest per Kumar
- More concise commit message in patch 1/2
- v1 link: https://lore.kernel.org/all/20260320160055.4114055-1-wusa...
Samuel Wu (2):
PM: wakeup: Add kfuncs to traverse over wakeup_sources
selftests/bpf: Add tests for wakeup_sources kfuncs
drivers/base/power/power.h | 7 ++
drivers/base/power/wakeup.c | 72 +++++++++++-
tools/testing/selftests/bpf/config | 3 +-
.../selftests/bpf/prog_tests/wakeup_source.c | 101 +++++++++++++++++
.../selftests/bpf/progs/test_wakeup_source.c | 107 ++++++++++++++++++
.../selftests/bpf/progs/wakeup_source.h | 22 ++++
.../selftests/bpf/progs/wakeup_source_fail.c | 63 +++++++++++
7 files changed, 372 insertions(+), 3 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/wakeup_source.c
create mode 100644 tools/testing/selftests/bpf/progs/test_wakeup_source.c
create mode 100644 tools/testing/selftests/bpf/progs/wakeup_source.h
create mode 100644 tools/testing/selftests/bpf/progs/wakeup_source_fail.c
--
2.53.0.1018.g2bb0e51243-goog
