diff options
| author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2009-04-24 07:27:05 +0400 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2009-04-24 08:08:38 +0400 |
| commit | 334d4169a6592d3fcd863bbe822a8f6985ffa9af (patch) | |
| tree | 3ac9c038304eaa69b06d9cac735fd62a8d6c47b3 /include/linux/ring_buffer.h | |
| parent | c2518c4366f087ebc10b3919cb2461bbe4f42d0c (diff) | |
| download | linux-334d4169a6592d3fcd863bbe822a8f6985ffa9af.tar.xz | |
ring_buffer: compressed event header
RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes
an 'u32' to save the actually length for events which data size > 28.
This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA.
[ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ]
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <49F13189.3090000@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/ring_buffer.h')
| -rw-r--r-- | include/linux/ring_buffer.h | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index fac8f1ac6f49..1c2f80911fbe 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -11,7 +11,7 @@ struct ring_buffer_iter; * Don't refer to this struct directly, use functions below. */ struct ring_buffer_event { - u32 type:2, len:3, time_delta:27; + u32 type_len:5, time_delta:27; u32 array[]; }; @@ -24,7 +24,8 @@ struct ring_buffer_event { * size is variable depending on how much * padding is needed * If time_delta is non zero: - * everything else same as RINGBUF_TYPE_DATA + * array[0] holds the actual length + * size = 4 + length (bytes) * * @RINGBUF_TYPE_TIME_EXTEND: Extend the time delta * array[0] = time delta (28 .. 59) @@ -35,22 +36,23 @@ struct ring_buffer_event { * array[1..2] = tv_sec * size = 16 bytes * - * @RINGBUF_TYPE_DATA: Data record - * If len is zero: + * <= @RINGBUF_TYPE_DATA_TYPE_LEN_MAX: + * Data record + * If type_len is zero: * array[0] holds the actual length * array[1..(length+3)/4] holds data - * size = 4 + 4 + length (bytes) + * size = 4 + length (bytes) * else - * length = len << 2 + * length = type_len << 2 * array[0..(length+3)/4-1] holds data * size = 4 + length (bytes) */ enum ring_buffer_type { + RINGBUF_TYPE_DATA_TYPE_LEN_MAX = 28, RINGBUF_TYPE_PADDING, RINGBUF_TYPE_TIME_EXTEND, /* FIXME: RINGBUF_TYPE_TIME_STAMP not implemented */ RINGBUF_TYPE_TIME_STAMP, - RINGBUF_TYPE_DATA, }; unsigned ring_buffer_event_length(struct ring_buffer_event *event); |