Commit-ID: c8d771835e18c938dae8690611d65fe98ad30f58
Gitweb: http://git.kernel.org/tip/c8d771835e18c938dae8690611d65fe98ad30f58
Author: Steven Rostedt <srostedt@xxxxxxxxxx>
AuthorDate: Wed, 29 Apr 2009 18:03:45 -0400
Committer: Steven Rostedt <rostedt@xxxxxxxxxxx>
CommitDate: Tue, 5 May 2009 13:52:02 -0400
tracing: export stats of ring buffers to userspace
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 <rostedt@xxxxxxxxxxx>
---
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
--
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