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tracing: expand the ring buffers when an event is activated

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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: Steven Rostedt <srostedt@redhat.com>
This commit is contained in:
Steven Rostedt 2009-03-11 14:33:00 -04:00
parent 73c5162aa3
commit 1852fcce18
3 changed files with 31 additions and 0 deletions
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20
kernel/trace/trace.c
View File

@ -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 *

3
kernel/trace/trace.h
View File

@ -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,

8
kernel/trace/trace_events.c
View File

@ -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: