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#!/usr/bin/python

# Copyright (c) PLUMgrid, Inc.

# Licensed under the Apache License, Version 2.0 (the "License")

from bcc import BPF

from time import sleep

b = BPF(text="""

#include <uapi/linux/ptrace.h>

#include <linux/sched.h>

struct key_t {

u32 prev_pid;

u32 curr_pid;

};

// map_type, key_type, leaf_type, table_name, num_entry

BPF_HASH(stats, struct key_t, u64, 1024);

int count_sched(struct pt_regs *ctx, struct task_struct *prev) {

struct key_t key = {};

u64 zero = 0, *val;

key.curr_pid = bpf_get_current_pid_tgid();

key.prev_pid = prev->pid;

val = stats.lookup_or_init(&key, &zero);

(*val)++;

return 0;

}

""")

b.attach_kprobe(event="finish_task_switch", fn_name="count_sched")

# generate many schedule events

for i in range(0, 100): sleep(0.01)

for k, v in b["stats"].items():

print("task_switch[%5d->%5d]=%u" % (k.prev_pid, k.curr_pid, v.value))