tracing: Add tracefs file buffer_percentage
Add a "buffer_percentage" file, that allows users to specify how much of the
buffer (percentage of pages) need to be filled before waking up a task
blocked on a per cpu trace_pipe_raw file.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 48d5eb2..d382fd1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6948,7 +6948,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK))
goto out;
- ret = wait_on_pipe(iter, 1);
+ ret = wait_on_pipe(iter, iter->tr->buffer_percent);
if (ret)
goto out;
@@ -7662,6 +7662,53 @@ static const struct file_operations rb_simple_fops = {
.llseek = default_llseek,
};
+static ssize_t
+buffer_percent_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct trace_array *tr = filp->private_data;
+ char buf[64];
+ int r;
+
+ r = tr->buffer_percent;
+ r = sprintf(buf, "%d\n", r);
+
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+buffer_percent_write(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct trace_array *tr = filp->private_data;
+ unsigned long val;
+ int ret;
+
+ ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
+ if (ret)
+ return ret;
+
+ if (val > 100)
+ return -EINVAL;
+
+ if (!val)
+ val = 1;
+
+ tr->buffer_percent = val;
+
+ (*ppos)++;
+
+ return cnt;
+}
+
+static const struct file_operations buffer_percent_fops = {
+ .open = tracing_open_generic_tr,
+ .read = buffer_percent_read,
+ .write = buffer_percent_write,
+ .release = tracing_release_generic_tr,
+ .llseek = default_llseek,
+};
+
struct dentry *trace_instance_dir;
static void
@@ -7970,6 +8017,11 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
trace_create_file("timestamp_mode", 0444, d_tracer, tr,
&trace_time_stamp_mode_fops);
+ tr->buffer_percent = 1;
+
+ trace_create_file("buffer_percent", 0444, d_tracer,
+ tr, &buffer_percent_fops);
+
create_trace_options_dir(tr);
#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)