diff options
Diffstat (limited to 'tools/perf/util/bpf_skel/off_cpu.bpf.c')
| -rw-r--r-- | tools/perf/util/bpf_skel/off_cpu.bpf.c | 283 |
1 files changed, 283 insertions, 0 deletions
diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c new file mode 100644 index 000000000..38e3b287d --- /dev/null +++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c @@ -0,0 +1,283 @@ +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +// Copyright (c) 2022 Google +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> +#include <bpf/bpf_core_read.h> + +/* task->flags for off-cpu analysis */ +#define PF_KTHREAD 0x00200000 /* I am a kernel thread */ + +/* task->state for off-cpu analysis */ +#define TASK_INTERRUPTIBLE 0x0001 +#define TASK_UNINTERRUPTIBLE 0x0002 + +/* create a new thread */ +#define CLONE_THREAD 0x10000 + +#define MAX_STACKS 32 +#define MAX_ENTRIES 102400 + +struct tstamp_data { + __u32 stack_id; + __u32 state; + __u64 timestamp; +}; + +struct offcpu_key { + __u32 pid; + __u32 tgid; + __u32 stack_id; + __u32 state; + __u64 cgroup_id; +}; + +struct { + __uint(type, BPF_MAP_TYPE_STACK_TRACE); + __uint(key_size, sizeof(__u32)); + __uint(value_size, MAX_STACKS * sizeof(__u64)); + __uint(max_entries, MAX_ENTRIES); +} stacks SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_TASK_STORAGE); + __uint(map_flags, BPF_F_NO_PREALLOC); + __type(key, int); + __type(value, struct tstamp_data); +} tstamp SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_HASH); + __uint(key_size, sizeof(struct offcpu_key)); + __uint(value_size, sizeof(__u64)); + __uint(max_entries, MAX_ENTRIES); +} off_cpu SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_HASH); + __uint(key_size, sizeof(__u32)); + __uint(value_size, sizeof(__u8)); + __uint(max_entries, 1); +} cpu_filter SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_HASH); + __uint(key_size, sizeof(__u32)); + __uint(value_size, sizeof(__u8)); + __uint(max_entries, 1); +} task_filter SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_HASH); + __uint(key_size, sizeof(__u64)); + __uint(value_size, sizeof(__u8)); + __uint(max_entries, 1); +} cgroup_filter SEC(".maps"); + +/* new kernel task_struct definition */ +struct task_struct___new { + long __state; +} __attribute__((preserve_access_index)); + +/* old kernel task_struct definition */ +struct task_struct___old { + long state; +} __attribute__((preserve_access_index)); + +int enabled = 0; +int has_cpu = 0; +int has_task = 0; +int has_cgroup = 0; +int uses_tgid = 0; + +const volatile bool has_prev_state = false; +const volatile bool needs_cgroup = false; +const volatile bool uses_cgroup_v1 = false; + +int perf_subsys_id = -1; + +/* + * Old kernel used to call it task_struct->state and now it's '__state'. + * Use BPF CO-RE "ignored suffix rule" to deal with it like below: + * + * https://nakryiko.com/posts/bpf-core-reference-guide/#handling-incompatible-field-and-type-changes + */ +static inline int get_task_state(struct task_struct *t) +{ + /* recast pointer to capture new type for compiler */ + struct task_struct___new *t_new = (void *)t; + + if (bpf_core_field_exists(t_new->__state)) { + return BPF_CORE_READ(t_new, __state); + } else { + /* recast pointer to capture old type for compiler */ + struct task_struct___old *t_old = (void *)t; + + return BPF_CORE_READ(t_old, state); + } +} + +static inline __u64 get_cgroup_id(struct task_struct *t) +{ + struct cgroup *cgrp; + + if (!uses_cgroup_v1) + return BPF_CORE_READ(t, cgroups, dfl_cgrp, kn, id); + + if (perf_subsys_id == -1) { +#if __has_builtin(__builtin_preserve_enum_value) + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id, + perf_event_cgrp_id); +#else + perf_subsys_id = perf_event_cgrp_id; +#endif + } + + cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_subsys_id], cgroup); + return BPF_CORE_READ(cgrp, kn, id); +} + +static inline int can_record(struct task_struct *t, int state) +{ + /* kernel threads don't have user stack */ + if (t->flags & PF_KTHREAD) + return 0; + + if (state != TASK_INTERRUPTIBLE && + state != TASK_UNINTERRUPTIBLE) + return 0; + + if (has_cpu) { + __u32 cpu = bpf_get_smp_processor_id(); + __u8 *ok; + + ok = bpf_map_lookup_elem(&cpu_filter, &cpu); + if (!ok) + return 0; + } + + if (has_task) { + __u8 *ok; + __u32 pid; + + if (uses_tgid) + pid = t->tgid; + else + pid = t->pid; + + ok = bpf_map_lookup_elem(&task_filter, &pid); + if (!ok) + return 0; + } + + if (has_cgroup) { + __u8 *ok; + __u64 cgrp_id = get_cgroup_id(t); + + ok = bpf_map_lookup_elem(&cgroup_filter, &cgrp_id); + if (!ok) + return 0; + } + + return 1; +} + +static int off_cpu_stat(u64 *ctx, struct task_struct *prev, + struct task_struct *next, int state) +{ + __u64 ts; + __u32 stack_id; + struct tstamp_data *pelem; + + ts = bpf_ktime_get_ns(); + + if (!can_record(prev, state)) + goto next; + + stack_id = bpf_get_stackid(ctx, &stacks, + BPF_F_FAST_STACK_CMP | BPF_F_USER_STACK); + + pelem = bpf_task_storage_get(&tstamp, prev, NULL, + BPF_LOCAL_STORAGE_GET_F_CREATE); + if (!pelem) + goto next; + + pelem->timestamp = ts; + pelem->state = state; + pelem->stack_id = stack_id; + +next: + pelem = bpf_task_storage_get(&tstamp, next, NULL, 0); + + if (pelem && pelem->timestamp) { + struct offcpu_key key = { + .pid = next->pid, + .tgid = next->tgid, + .stack_id = pelem->stack_id, + .state = pelem->state, + .cgroup_id = needs_cgroup ? get_cgroup_id(next) : 0, + }; + __u64 delta = ts - pelem->timestamp; + __u64 *total; + + total = bpf_map_lookup_elem(&off_cpu, &key); + if (total) + *total += delta; + else + bpf_map_update_elem(&off_cpu, &key, &delta, BPF_ANY); + + /* prevent to reuse the timestamp later */ + pelem->timestamp = 0; + } + + return 0; +} + +SEC("tp_btf/task_newtask") +int on_newtask(u64 *ctx) +{ + struct task_struct *task; + u64 clone_flags; + u32 pid; + u8 val = 1; + + if (!uses_tgid) + return 0; + + task = (struct task_struct *)bpf_get_current_task(); + + pid = BPF_CORE_READ(task, tgid); + if (!bpf_map_lookup_elem(&task_filter, &pid)) + return 0; + + task = (struct task_struct *)ctx[0]; + clone_flags = ctx[1]; + + pid = task->tgid; + if (!(clone_flags & CLONE_THREAD)) + bpf_map_update_elem(&task_filter, &pid, &val, BPF_NOEXIST); + + return 0; +} + +SEC("tp_btf/sched_switch") +int on_switch(u64 *ctx) +{ + struct task_struct *prev, *next; + int prev_state; + + if (!enabled) + return 0; + + prev = (struct task_struct *)ctx[1]; + next = (struct task_struct *)ctx[2]; + + if (has_prev_state) + prev_state = (int)ctx[3]; + else + prev_state = get_task_state(prev); + + return off_cpu_stat(ctx, prev, next, prev_state); +} + +char LICENSE[] SEC("license") = "Dual BSD/GPL"; |