Messages in this thread Patch in this message | | | Date | Thu, 25 Jul 2013 10:28:27 +0800 | From | Li Zefan <> | Subject | [PATCH 2/2][RESEND] tracing: Shrink the size of struct ftrace_event_field |
| |
Use bit fields, and the size of struct ftrace_event_field can be shrunk from 48 bytes to 40 bytes on 64bit kernel.
slab_name active_obj nr_obj size obj_per_slab --------------------------------------------- ftrace_event_field 1105 1105 48 85 (before) ftrace_event_field 1224 1224 40 102 (after)
This saves a few Kbytes: (1224 * 40) - (1105 * 48) = 4080
Signed-off-by: Li Zefan <lizefan@huawei.com> --- kernel/trace/trace.h | 8 ++++---- kernel/trace/trace_events.c | 5 +++++ 2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 9e01458..a3365a4 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -916,10 +916,10 @@ struct ftrace_event_field { struct list_head link; const char *name; const char *type; - int filter_type; - int offset; - int size; - int is_signed; + unsigned int filter_type:4; + unsigned int offset:12; + unsigned int size:12; + unsigned int is_signed:1; }; struct event_filter { diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 53582e9..67aee85 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -111,6 +111,11 @@ static int __trace_define_field(struct list_head *head, const char *type, field->size = size; field->is_signed = is_signed; + WARN_ON(offset >= (1 << 12)); + WARN_ON(size >= (1 << 12)); + WARN_ON(is_signed >= (1 << 1)); + WARN_ON(field->filter_type >= (1 << 4)); + list_add(&field->link, head); return 0; -- 1.8.0.2
| |