/*
 * vfsreadlat.c        VFS read latency distribution.
 *            For Linux, uses BCC, eBPF. See .py file.
 *
 * Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * 15-Aug-2015    Brendan Gregg    Created this.
 */

#include <uapi/linux/ptrace.h>

BPF_HASH(start, u32);
BPF_HISTOGRAM(dist);

int do_entry(struct pt_regs *ctx)
{
    u32 pid;
    u64 ts, *val;

    pid = bpf_get_current_pid_tgid();
    ts = bpf_ktime_get_ns();
    start.update(&pid, &ts);
    return 0;
}

int do_return(struct pt_regs *ctx)
{
    u32 pid;
    u64 *tsp, delta;

    pid = bpf_get_current_pid_tgid();
    tsp = start.lookup(&pid);

    if (tsp != 0) {
        delta = bpf_ktime_get_ns() - *tsp;
        dist.increment(bpf_log2l(delta / 1000));
        start.delete(&pid);
    }

    return 0;
}