From b382ede6b5eb8188926b72a9ef42fd2354342a97 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 10 Oct 2012 21:44:34 -0400 Subject: [PATCH] tracing: Expand ring buffer when trace_printk() is used Since tracing is not used by 99% of Linux users, even though tracing may be configured in, it does not make sense to allocate 1.4 Megs per CPU for the ring buffers if they are not used. Thus, on boot up the ring buffers are set to a minimal size until something needs the and they are expanded. This works well for events and tracers (function, etc), but for the asynchronous use of trace_printk() which can write to the ring buffer at any time, does not expand the buffers. On boot up a check is made to see if any trace_printk() is used to see if the trace_printk() temp buffer pages should be allocated. This same code can be used to expand the buffers as well. Suggested-by: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 36c213f..a5411b7 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1571,6 +1571,9 @@ void trace_printk_init_buffers(void) pr_info("ftrace: Allocated trace_printk buffers\n"); + /* Expand the buffers to set size */ + tracing_update_buffers(); + buffers_allocated = 1; } @@ -3030,6 +3033,10 @@ static int __tracing_resize_ring_buffer(unsigned long size, int cpu) */ ring_buffer_expanded = 1; + /* May be called before buffers are initialized */ + if (!global_trace.buffer) + return 0; + ret = ring_buffer_resize(global_trace.buffer, size, cpu); if (ret < 0) return ret; -- 2.7.4