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, and a kfunc to get head of wakeup sources list is needed to start traversing the list. 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/[email protected]/ Changes in v4: - Removed `.owner = THIS_MODULE` for btf_kfunc_id_set per Greg - Add a graceful exit in selftest if bpf_wakeup_sources_get_head() is not present due to kernel configs without CONFIG_PM_SLEEP (e.g. s390) - Relaxed substr match in wakeup_source_unlock_null() selftest - v3 link: https://lore.kernel.org/all/[email protected]/ Changes in v3: - Changed return type of bpf_wakeup_sources_get_head() to `void *` per Alexei - Added failure test for direct dereference of wakeup source head - Use bpf_core_cast() instead of macros in BPF program per Kumar - v2 link: https://lore.kernel.org/all/[email protected]/ 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/[email protected]/ 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 | 71 ++++++++++- tools/testing/selftests/bpf/config | 3 +- .../selftests/bpf/prog_tests/wakeup_source.c | 118 ++++++++++++++++++ .../selftests/bpf/progs/test_wakeup_source.c | 92 ++++++++++++++ .../selftests/bpf/progs/wakeup_source.h | 22 ++++ .../selftests/bpf/progs/wakeup_source_fail.c | 76 +++++++++++ 7 files changed, 386 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 -- 2.54.0.563.g4f69b47b94-goog
