[PATCH] tracing/events: change the type of __str_loc_item to unsigned short

[PATCH] tracing/events: change the type of __str_loc_item to unsigned short

[Li Zefan]

When defining a dynamic size string, we add __str_loc_##item to the
trace entry, and it stores the location of the actual string in
entry->_str_data[]

'unsigned short' should be sufficient to store this information, thus
we save 2 bytes per dyn-size string in the ring buffer.

[ Impact: reduce memory occupied by dyn-size strings in ring buffer ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 include/trace/ftrace.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index edb02bc..b5ff2e8 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -25,7 +25,7 @@
 #define __field(type, item)		type	item;
 
 #undef __string
-#define __string(item, src)		int	__str_loc_##item;
+#define __string(item, src)		unsigned short	__str_loc_##item;
 
 #undef TP_STRUCT__entry
 #define TP_STRUCT__entry(args...) args
-- 1.5.4.rc3 

Re: [PATCH] tracing/events: change the type of __str_loc_item to unsigned short

[Frederic Weisbecker]

On Thu, May 21, 2009 at 01:59:18PM +0800, Li Zefan wrote:
> When defining a dynamic size string, we add __str_loc_##item to the
> trace entry, and it stores the location of the actual string in
> entry->_str_data[]
> 
> 'unsigned short' should be sufficient to store this information, thus
> we save 2 bytes per dyn-size string in the ring buffer.
> 
> [ Impact: reduce memory occupied by dyn-size strings in ring buffer ]
> 
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> ---
>  include/trace/ftrace.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> index edb02bc..b5ff2e8 100644
> --- a/include/trace/ftrace.h
> +++ b/include/trace/ftrace.h
> @@ -25,7 +25,7 @@
>  #define __field(type, item)		type	item;
>  
>  #undef __string
> -#define __string(item, src)		int	__str_loc_##item;
> +#define __string(item, src)		unsigned short	__str_loc_##item;
>  
>  #undef TP_STRUCT__entry
>  #define TP_STRUCT__entry(args...) args
> -- 1.5.4.rc3 


Yeah, a max length of about 32000 is sufficient, the filter
engine is bounded to MAX_FILTER_STR_VAL anyway :)

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

[tip:tracing/core] tracing/events: change the type of __str_loc_item to unsigned short

[tip-bot for Li Zefan]

Commit-ID:  b0aae68cc5508f3c2fbf728988c954db4c8b8a53
Gitweb:     http://git.kernel.org/tip/b0aae68cc5508f3c2fbf728988c954db4c8b8a53
Author:     Li Zefan <lizf@cn.fujitsu.com>
AuthorDate: Thu, 21 May 2009 13:59:18 +0800
Committer:  Frederic Weisbecker <fweisbec@gmail.com>
CommitDate: Tue, 26 May 2009 00:15:21 +0200

tracing/events: change the type of __str_loc_item to unsigned short

When defining a dynamic size string, we add __str_loc_##item to the
trace entry, and it stores the location of the actual string in
entry->_str_data[]

'unsigned short' should be sufficient to store this information, thus
we save 2 bytes per dyn-size string in the ring buffer.

[ Impact: reduce memory occupied by dyn-size strings in ring buffer ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A14EDB6.2050507@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>


---
 include/trace/ftrace.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index edb02bc..b5ff2e8 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -25,7 +25,7 @@
 #define __field(type, item)		type	item;
 
 #undef __string
-#define __string(item, src)		int	__str_loc_##item;
+#define __string(item, src)		unsigned short	__str_loc_##item;
 
 #undef TP_STRUCT__entry
 #define TP_STRUCT__entry(args...) args