From: Steven Rostedt This patch adds stats to the ftrace ring buffers: # cat /debugfs/tracing/per_cpu/cpu0/stats entries: 42360 overrun: 30509326 commit overrun: 0 nmi dropped: 0 Where entries are the total number of data entries in the buffer. overrun is the number of entries not consumed and were overwritten by the writer. commit overrun is the number of entries dropped due to nested writers wrapping the buffer before the initial writer finished the commit. nmi dropped is the number of entries dropped due to the ring buffer lock being held when an nmi was going to write to the ring buffer. Note, this field will be meaningless and will go away when the ring buffer becomes lockless. [ Impact: let userspace know what is happening in the ring buffers ] Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 42 insertions(+), 0 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index f5427e0..74df029 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3595,6 +3595,45 @@ static const struct file_operations tracing_buffers_fops = { .llseek = no_llseek, }; +static ssize_t +tracing_stats_read(struct file *filp, char __user *ubuf, + size_t count, loff_t *ppos) +{ + unsigned long cpu = (unsigned long)filp->private_data; + struct trace_array *tr = &global_trace; + struct trace_seq *s; + unsigned long cnt; + + s = kmalloc(sizeof(*s), GFP_ATOMIC); + if (!s) + return ENOMEM; + + trace_seq_init(s); + + cnt = ring_buffer_entries_cpu(tr->buffer, cpu); + trace_seq_printf(s, "entries: %ld\n", cnt); + + cnt = ring_buffer_overrun_cpu(tr->buffer, cpu); + trace_seq_printf(s, "overrun: %ld\n", cnt); + + cnt = ring_buffer_commit_overrun_cpu(tr->buffer, cpu); + trace_seq_printf(s, "commit overrun: %ld\n", cnt); + + cnt = ring_buffer_nmi_dropped_cpu(tr->buffer, cpu); + trace_seq_printf(s, "nmi dropped: %ld\n", cnt); + + count = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len); + + kfree(s); + + return count; +} + +static const struct file_operations tracing_stats_fops = { + .open = tracing_open_generic, + .read = tracing_stats_read, +}; + #ifdef CONFIG_DYNAMIC_FTRACE int __weak ftrace_arch_read_dyn_info(char *buf, int size) @@ -3708,6 +3747,9 @@ static void tracing_init_debugfs_percpu(long cpu) trace_create_file("trace_pipe_raw", 0444, d_cpu, (void *) cpu, &tracing_buffers_fops); + + trace_create_file("stats", 0444, d_cpu, + (void *) cpu, &tracing_stats_fops); } #ifdef CONFIG_FTRACE_SELFTEST -- 1.6.2.4 -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/