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    Subject[PATCH 13/18] tracing: Add kprobes event profiling interface
    Date
    From: Masami Hiramatsu <mhiramat@redhat.com>

    Add profiling interfaces for each kprobes event. This interface provides
    how many times each probe hit or missed.

    Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
    Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
    Cc: Avi Kivity <avi@redhat.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Frank Ch. Eigler <fche@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Jason Baron <jbaron@redhat.com>
    Cc: Jim Keniston <jkenisto@us.ibm.com>
    Cc: K.Prasad <prasad@linux.vnet.ibm.com>
    Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
    Cc: Li Zefan <lizf@cn.fujitsu.com>
    Cc: Przemysław Pawełczyk <przemyslaw@pawelczyk.it>
    Cc: Roland McGrath <roland@redhat.com>
    Cc: Sam Ravnborg <sam@ravnborg.org>
    Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Tom Zanussi <tzanussi@gmail.com>
    Cc: Vegard Nossum <vegard.nossum@gmail.com>
    LKML-Reference: <20090813203541.31965.8452.stgit@localhost.localdomain>
    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    ---
    Documentation/trace/kprobetrace.txt | 8 ++++++
    kernel/trace/trace_kprobe.c | 43 +++++++++++++++++++++++++++++++++++
    2 files changed, 51 insertions(+), 0 deletions(-)

    diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
    index 5e59e85..3de7517 100644
    --- a/Documentation/trace/kprobetrace.txt
    +++ b/Documentation/trace/kprobetrace.txt
    @@ -70,6 +70,14 @@ filter:
    names and field names for describing filters.


    +Event Profiling
    +---------------
    + You can check the total number of probe hits and probe miss-hits via
    +/sys/kernel/debug/tracing/kprobe_profile.
    + The first column is event name, the second is the number of probe hits,
    +the third is the number of probe miss-hits.
    +
    +
    Usage examples
    --------------
    To add a probe as a new event, write a new definition to kprobe_events
    diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
    index 9c067bf..ce68197 100644
    --- a/kernel/trace/trace_kprobe.c
    +++ b/kernel/trace/trace_kprobe.c
    @@ -184,6 +184,7 @@ struct trace_probe {
    struct kprobe kp;
    struct kretprobe rp;
    };
    + unsigned long nhit;
    const char *symbol; /* symbol name */
    struct ftrace_event_call call;
    struct trace_event event;
    @@ -781,6 +782,37 @@ static const struct file_operations kprobe_events_ops = {
    .write = probes_write,
    };

    +/* Probes profiling interfaces */
    +static int probes_profile_seq_show(struct seq_file *m, void *v)
    +{
    + struct trace_probe *tp = v;
    +
    + seq_printf(m, " %-44s %15lu %15lu\n", tp->call.name, tp->nhit,
    + probe_is_return(tp) ? tp->rp.kp.nmissed : tp->kp.nmissed);
    +
    + return 0;
    +}
    +
    +static const struct seq_operations profile_seq_op = {
    + .start = probes_seq_start,
    + .next = probes_seq_next,
    + .stop = probes_seq_stop,
    + .show = probes_profile_seq_show
    +};
    +
    +static int profile_open(struct inode *inode, struct file *file)
    +{
    + return seq_open(file, &profile_seq_op);
    +}
    +
    +static const struct file_operations kprobe_profile_ops = {
    + .owner = THIS_MODULE,
    + .open = profile_open,
    + .read = seq_read,
    + .llseek = seq_lseek,
    + .release = seq_release,
    +};
    +
    /* Kprobe handler */
    static __kprobes int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
    {
    @@ -791,6 +823,8 @@ static __kprobes int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
    unsigned long irq_flags;
    struct ftrace_event_call *call = &tp->call;

    + tp->nhit++;
    +
    local_save_flags(irq_flags);
    pc = preempt_count();

    @@ -1140,9 +1174,18 @@ static __init int init_kprobe_trace(void)
    entry = debugfs_create_file("kprobe_events", 0644, d_tracer,
    NULL, &kprobe_events_ops);

    + /* Event list interface */
    if (!entry)
    pr_warning("Could not create debugfs "
    "'kprobe_events' entry\n");
    +
    + /* Profile interface */
    + entry = debugfs_create_file("kprobe_profile", 0444, d_tracer,
    + NULL, &kprobe_profile_ops);
    +
    + if (!entry)
    + pr_warning("Could not create debugfs "
    + "'kprobe_profile' entry\n");
    return 0;
    }
    fs_initcall(init_kprobe_trace);
    --
    1.6.2.3
    --
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