Commit a94c80e7 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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ftrace: rename trace_entries to buffer_size_kb 



Impact: rename of debugfs file trace_entries to buffer_size_kb

The original ftrace had fixed size entries, and the number of entries
was shown and modified via the file called trace_entries. By converting
to the unified trace buffer, we now allow for variable size entries
which makes the meaning of trace_entries pointless.

Since trace_size might be confused to the size of the trace, this patch
names it "buffer_size_kb" (thanks to Arjan van de Ven for this idea).

[ mingo@elte.hu: changed from buffer_size to buffer_size_kb ]

( Note, the units are still bytes - the next patch changes that,
  to keep the wide rename patch separate from the unit-change patch. )

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 24de3862

Documentation/ftrace.txt

+9 −9
Original line number Diff line number Diff line
@@ -94,7 +94,7 @@ of ftrace. Here is a list of some of the key files: 
		only be recorded if the latency is greater than

		the value in this file. (in microseconds)



  trace_entries: This sets or displays the number of bytes each CPU

  buffer_size_kb: This sets or displays the number of bytes each CPU

		buffer can hold. The tracer buffers are the same size

		for each CPU. The displayed number is the size of the

		 CPU buffer and not total size of all buffers. The
@@ -1299,13 +1299,13 @@ trace entries 
-------------



Having too much or not enough data can be troublesome in diagnosing

an issue in the kernel. The file trace_entries is used to modify

an issue in the kernel. The file buffer_size_kb is used to modify

the size of the internal trace buffers. The number listed

is the number of entries that can be recorded per CPU. To know

the full size, multiply the number of possible CPUS with the

number of entries.



 # cat /debug/tracing/trace_entries

 # cat /debug/tracing/buffer_size_kb

65620



Note, to modify this, you must have tracing completely disabled. To do that,
@@ -1313,8 +1313,8 @@ echo "nop" into the current_tracer. If the current_tracer is not set 
to "nop", an EINVAL error will be returned.



 # echo nop > /debug/tracing/current_tracer

 # echo 100000 > /debug/tracing/trace_entries

 # cat /debug/tracing/trace_entries

 # echo 100000 > /debug/tracing/buffer_size_kb

 # cat /debug/tracing/buffer_size_kb

100045
@@ -1323,8 +1323,8 @@ are held in individual pages. It allocates the number of pages it takes 
to fulfill the request. If more entries may fit on the last page

then they will be added.



 # echo 1 > /debug/tracing/trace_entries

 # cat /debug/tracing/trace_entries

 # echo 1 > /debug/tracing/buffer_size_kb

 # cat /debug/tracing/buffer_size_kb

85



This shows us that 85 entries can fit in a single page.
@@ -1332,8 +1332,8 @@ This shows us that 85 entries can fit in a single page. 
The number of pages which will be allocated is limited to a percentage

of available memory. Allocating too much will produce an error.



 # echo 1000000000000 > /debug/tracing/trace_entries

 # echo 1000000000000 > /debug/tracing/buffer_size_kb

-bash: echo: write error: Cannot allocate memory

 # cat /debug/tracing/trace_entries

 # cat /debug/tracing/buffer_size_kb

85

kernel/trace/trace.c

+2 −2
Original line number Diff line number Diff line
@@ -3198,11 +3198,11 @@ static __init int tracer_init_debugfs(void) 
		pr_warning("Could not create debugfs "

			   "'trace_pipe' entry\n");



	entry = debugfs_create_file("trace_entries", 0644, d_tracer,

	entry = debugfs_create_file("buffer_size_kb", 0644, d_tracer,

				    &global_trace, &tracing_entries_fops);

	if (!entry)

		pr_warning("Could not create debugfs "

			   "'trace_entries' entry\n");

			   "'buffer_size_kb' entry\n");



	entry = debugfs_create_file("trace_marker", 0220, d_tracer,

				    NULL, &tracing_mark_fops);

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