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Commit 03329f99 authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

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: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 2c2b0a78

kernel/trace/ring_buffer.c

+23 −16
Original line number Diff line number Diff line
@@ -489,6 +489,7 @@ struct ring_buffer_per_cpu { 
	local_t				commits;

	local_t				pages_touched;

	local_t				pages_read;

	long				last_pages_touch;

	size_t				shortest_full;

	unsigned long			read;

	unsigned long			read_bytes;
@@ -2632,7 +2633,9 @@ static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, 
static __always_inline void

rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)

{

	bool pagebusy;

	size_t nr_pages;

	size_t dirty;

	size_t full;



	if (buffer->irq_work.waiters_pending) {

		buffer->irq_work.waiters_pending = false;
@@ -2646,12 +2649,16 @@ rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) 
		irq_work_queue(&cpu_buffer->irq_work.work);

	}



	pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;

	if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))

		return;



	if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) {

		size_t nr_pages;

		size_t dirty;

		size_t full;

	if (cpu_buffer->reader_page == cpu_buffer->commit_page)

		return;



	if (!cpu_buffer->irq_work.full_waiters_pending)

		return;



	cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);



	full = cpu_buffer->shortest_full;

	nr_pages = cpu_buffer->nr_pages;
@@ -2664,7 +2671,6 @@ rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) 
	/* irq_work_queue() supplies it's own memory barriers */

	irq_work_queue(&cpu_buffer->irq_work.work);

}

}



/*

 * The lock and unlock are done within a preempt disable section.
@@ -4394,6 +4400,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) 
	local_set(&cpu_buffer->commits, 0);

	local_set(&cpu_buffer->pages_touched, 0);

	local_set(&cpu_buffer->pages_read, 0);

	cpu_buffer->last_pages_touch = 0;

	cpu_buffer->shortest_full = 0;

	cpu_buffer->read = 0;

	cpu_buffer->read_bytes = 0;

kernel/trace/trace.c

+53 −1
Original line number Diff line number Diff line
@@ -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)

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -247,6 +247,7 @@ struct trace_array { 
	int			clock_id;

	int			nr_topts;

	bool			clear_trace;

	int			buffer_percent;

	struct tracer		*current_trace;

	unsigned int		trace_flags;

	unsigned char		trace_flags_index[TRACE_FLAGS_MAX_SIZE];