Re: svn commit: r1907634 - /apr/apr/trunk/include/apr_buckets.h

Le 14/02/2023 à 11:51, Ivan Zhakov via dev a écrit :
> On Tue, 14 Feb 2023 at 10:58, <[email protected] 
> <mailto:[email protected]>> wrote:
> 
>     Author: jailletc36
>     Date: Tue Feb 14 07:56:50 2023
>     New Revision: 1907634
> 
>     URL: http://svn.apache.org/viewvc?rev=1907634&view=rev
>     <http://svn.apache.org/viewvc?rev=1907634&view=rev>
>     Log:
>     Re-order the fields of 'struct apr_bucket_file' to avoid a hole and
>     some padding.
> 
>     Before the patch, pahole states that:
> 
>     struct apr_bucket_file {
>              apr_bucket_refcount        refcount;             /*     0 
>         4 */
> 
>              /* XXX 4 bytes hole, try to pack */
> 
>              apr_file_t *               fd;                   /*     8 
>         8 */
>              apr_pool_t *               readpool;             /*    16 
>         8 */
>              int                        can_mmap;             /*    24 
>         4 */
> 
>              /* XXX 4 bytes hole, try to pack */
> 
>              apr_size_t                 read_size;            /*    32 
>         8 */
> 
>              /* size: 40, cachelines: 1, members: 5 */
>              /* sum members: 32, holes: 2, sum holes: 8 */
>              /* last cacheline: 40 bytes */
>     };
> 
> Nice, but I'd like to note that this change breaks ABI and can be 
> released only in APR 2.0.
> 

Sure.

I was just wondering if such small optimizations make sense or not.
It potentially makes backport of some other patches more difficult and 
breaks ABI.

So, does it worth the effort?

I've spotted a few of them in APR, and would make sure that such patches 
are welcomed before committing other things.

CJ

> 
> 
> -- 
> Ivan Zhakov