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Commit 1852fcce authored by Steven Rostedt's avatar Steven Rostedt
Browse files

tracing: expand the ring buffers when an event is activated 



To save memory, the tracer ring buffers are set to a minimum.
The activating of a trace expands the ring buffer size. This patch
adds this expanding, when an event is activated.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent 73c5162a

kernel/trace/trace.c

+20 −0
Original line number Diff line number Diff line
@@ -2357,6 +2357,26 @@ static int tracing_resize_ring_buffer(unsigned long size) 
	return ret;

}



/**

 * tracing_update_buffers - used by tracing facility to expand ring buffers

 *

 * To save on memory when the tracing is never used on a system with it

 * configured in. The ring buffers are set to a minimum size. But once

 * a user starts to use the tracing facility, then they need to grow

 * to their default size.

 *

 * This function is to be called when a tracer is about to be used.

 */

int tracing_update_buffers(void)

{

	int ret = 0;



	if (!ring_buffer_expanded)

		ret = tracing_resize_ring_buffer(trace_buf_size);



	return ret;

}



struct trace_option_dentry;



static struct trace_option_dentry *

kernel/trace/trace.h

+3 −0
Original line number Diff line number Diff line
@@ -737,6 +737,9 @@ static inline void trace_branch_disable(void) 
}

#endif /* CONFIG_BRANCH_TRACER */



/* set ring buffers to default size if not already done so */

int tracing_update_buffers(void);



/* trace event type bit fields, not numeric */

enum {

	TRACE_EVENT_TYPE_PRINTF		= 1,

kernel/trace/trace_events.c

+8 −0
Original line number Diff line number Diff line
@@ -141,6 +141,10 @@ ftrace_event_write(struct file *file, const char __user *ubuf, 
	if (!cnt || cnt < 0)

		return 0;



	ret = tracing_update_buffers();

	if (ret < 0)

		return ret;



	ret = get_user(ch, ubuf++);

	if (ret)

		return ret;
@@ -331,6 +335,10 @@ event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt, 
	if (ret < 0)

		return ret;



	ret = tracing_update_buffers();

	if (ret < 0)

		return ret;



	switch (val) {

	case 0:

	case 1: