change log for rtems (2010-06-22)

[Joel Sherrill]

On 06/22/2010 08:49 PM, Chris Johns wrote:
> On 23/06/10 6:12 AM, rtems-vc at rtems.org wrote:
>    
>> diff -u rtems/cpukit/libcsupport/include/rtems/libio_.h:1.37 rtems/cpukit/libcsupport/include/rtems/libio_.h:1.38
>> --- rtems/cpukit/libcsupport/include/rtems/libio_.h:1.37	Mon Jun 14 08:35:45 2010
>> +++ rtems/cpukit/libcsupport/include/rtems/libio_.h	Tue Jun 22 15:03:41 2010
>> @@ -148,13 +148,7 @@
>>     *  Macro to free a node.
>>     */
>>
>> -#define rtems_filesystem_freenode( _node ) \
>> -  do { \
>> -    if ( (_node)->ops )\
>> -      if ( (_node)->ops->freenod_h ) \
>> -        (*(_node)->ops->freenod_h)( (_node) ); \
>> -  } while (0)
>> -
>> +void rtems_filesystem_freenode( rtems_filesystem_location_info_t*  node );
>>
>>      
> Why has this been done ?
>
> This code is a hot spot in the file system. Not all file systems need to
> free a node but they now suffer an extra call. Maybe the overhead is not
> too much but it does add up.
>
>    
It lead to horrible branch patch explosion and code size.   It introduced
a lot of paths that had to tested.  Look at the top two entries here:

http://www.rtems.org/ftp/pub/rtems/people/joel/coverage/erc32.html#OsPD

Code coverage went up about 4%!!! And the number of branches which
are executed but we have only taken one direction (e.g. always taken
or never taken) dropped from 727 to 626.

> Chris
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