cgroup: expose cpu.stat and io.stat to BPF - #1165
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Collecting cgroup statistics is expensive because the existing method opens and parses a cgroup file. memcg already provides an efficient BPF interface; extend that model to the CPU controller. Register css_rstat_flush() as a common kfunc and add bpf_cgroup_base_stat(). The latter returns cgroup_base_stat after the same cputime adjustment used by cpu.stat. The BPF program reads the plain CFS bandwidth counters directly. Add bpf_css_to_task_group() to check the controller and give the verifier a typed task_group pointer for bpf_per_cpu_ptr(). css_rstat_flush() may reschedule and requires a sleepable program. bpf_cgroup_base_stat() only takes locks and is not marked sleepable, but those locks are not NMI-safe. Suggested-by: Shakeel Butt <shakeel.butt@linux.dev> Suggested-by: Tejun Heo <tj@kernel.org> Assisted-by: Claude:claude-opus-5 Signed-off-by: Ziyang Men <ziyang.meme@gmail.com>
Add cgroup_iter_cpu, a selftest for the CPU controller BPF kfuncs.
The userspace side runs a CPU hog in a test cgroup with cpu.max settled
then:
- checks the CPU-time and throttling counters are nonzero,
- compares whether all values the program read are same as those
reading from cgroup file.
Enable CONFIG_CGROUP_SCHED, CONFIG_FAIR_GROUP_SCHED and
CONFIG_CFS_BANDWIDTH in the selftest config.
Tested on VM with v7.2-rc5.
Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
Assisted-by: Claude:claude-opus-5
Signed-off-by: Ziyang Men <ziyang.meme@gmail.com>
Collecting cgroup statistics is expensive because the existing method opens and parses a cgroup file for every cgroup. memcg already provides an efficient BPF interface; extend that model to the block controller. Add bpf_cgroup_css() and bpf_css_release() to acquire a controller's css from a cgroup. The reference keeps the css alive across the sleepable css_rstat_flush(). Add bpf_css_to_blkcg() as a checked RCU-protected css-to-blkcg conversion and an open-coded iterator for the per-device blkgs. Suggested-by: Shakeel Butt <shakeel.butt@linux.dev> Suggested-by: Tejun Heo <tj@kernel.org> Assisted-by: Claude:claude-opus-5 Signed-off-by: Ziyang Men <ziyang.meme@gmail.com>
Add cgroup_iter_io to test the blkcg io.stat BPF kfuncs. The BPF program acquires the I/O css, flushes its statistics, converts it to a typed blkcg under RCU, walks the blkgs, and releases the css reference. The test performs O_DIRECT I/O on a private loop device. It checks the device ID and counters against io.stat. Assisted-by: Claude:claude-opus-5 Signed-off-by: Ziyang Men <ziyang.meme@gmail.com>
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Pull request for series with
subject: cgroup: expose cpu.stat and io.stat to BPF
version: 3
url: https://patchwork.kernel.org/project/linux-block/list/?series=1149340