diff options
| -rw-r--r-- | Documentation/trace/ftrace.txt | 24 | ||||
| -rw-r--r-- | kernel/trace/trace.c | 47 |
2 files changed, 71 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt index d4601df6e72e..54213e5c23f6 100644 --- a/Documentation/trace/ftrace.txt +++ b/Documentation/trace/ftrace.txt @@ -539,6 +539,30 @@ of ftrace. Here is a list of some of the key files: See events.txt for more information. + timestamp_mode: + + Certain tracers may change the timestamp mode used when + logging trace events into the event buffer. Events with + different modes can coexist within a buffer but the mode in + effect when an event is logged determines which timestamp mode + is used for that event. The default timestamp mode is + 'delta'. + + Usual timestamp modes for tracing: + + # cat timestamp_mode + [delta] absolute + + The timestamp mode with the square brackets around it is the + one in effect. + + delta: Default timestamp mode - timestamp is a delta against + a per-buffer timestamp. + + absolute: The timestamp is a full timestamp, not a delta + against some other value. As such it takes up more + space and is less efficient. + hwlat_detector: Directory for the Hardware Latency Detector. diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index cba003f0362e..988d94a05e81 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4515,6 +4515,9 @@ static const char readme_msg[] = #ifdef CONFIG_X86_64 " x86-tsc: TSC cycle counter\n" #endif + "\n timestamp_mode\t-view the mode used to timestamp events\n" + " delta: Delta difference against a buffer-wide timestamp\n" + " absolute: Absolute (standalone) timestamp\n" "\n trace_marker\t\t- Writes into this file writes into the kernel buffer\n" "\n trace_marker_raw\t\t- Writes into this file writes binary data into the kernel buffer\n" " tracing_cpumask\t- Limit which CPUs to trace\n" @@ -6282,6 +6285,40 @@ static int tracing_clock_open(struct inode *inode, struct file *file) return ret; } +static int tracing_time_stamp_mode_show(struct seq_file *m, void *v) +{ + struct trace_array *tr = m->private; + + mutex_lock(&trace_types_lock); + + if (ring_buffer_time_stamp_abs(tr->trace_buffer.buffer)) + seq_puts(m, "delta [absolute]\n"); + else + seq_puts(m, "[delta] absolute\n"); + + mutex_unlock(&trace_types_lock); + + return 0; +} + +static int tracing_time_stamp_mode_open(struct inode *inode, struct file *file) +{ + struct trace_array *tr = inode->i_private; + int ret; + + if (tracing_disabled) + return -ENODEV; + + if (trace_array_get(tr)) + return -ENODEV; + + ret = single_open(file, tracing_time_stamp_mode_show, inode->i_private); + if (ret < 0) + trace_array_put(tr); + + return ret; +} + int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs) { int ret = 0; @@ -6560,6 +6597,13 @@ static const struct file_operations trace_clock_fops = { .write = tracing_clock_write, }; +static const struct file_operations trace_time_stamp_mode_fops = { + .open = tracing_time_stamp_mode_open, + .read = seq_read, + .llseek = seq_lseek, + .release = tracing_single_release_tr, +}; + #ifdef CONFIG_TRACER_SNAPSHOT static const struct file_operations snapshot_fops = { .open = tracing_snapshot_open, @@ -7882,6 +7926,9 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer) trace_create_file("tracing_on", 0644, d_tracer, tr, &rb_simple_fops); + trace_create_file("timestamp_mode", 0444, d_tracer, tr, + &trace_time_stamp_mode_fops); + create_trace_options_dir(tr); #if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER) |