Duy Nguyen <pclouds@xxxxxxxxx> wrote:
> which saves 12 bytes (or another 74 MB). 222 MB total is plenty of
> space to keep some file cache from being evicted.
Nice! I can definitely benefit from lower memory usage when
packing. Fwiw, I use pahole with other projects to help find
packing opportunities:
git://git.kernel.org/pub/scm/devel/pahole/pahole.git
> @@ -14,11 +26,10 @@ struct object_entry {
> void *delta_data; /* cached delta (uncompressed) */
> unsigned long delta_size; /* delta data size (uncompressed) */
> unsigned long z_delta_size; /* delta data size (compressed) */
> - enum object_type type;
> - enum object_type in_pack_type; /* could be delta */
> uint32_t hash; /* name hint hash */
> - unsigned int in_pack_pos;
> unsigned char in_pack_header_size;
> + unsigned type:3; /* enum object_type */
> + unsigned in_pack_type:3; /* enum object_type - could be delta */
For C99 compilers, enums can be bitfields. I introduced the
following macro into Ruby a few weeks ago to remain compatible
with non-C99 compilers:
/*
* For declaring bitfields out of non-unsigned int types:
* struct date {
* BITFIELD(enum months) month:4;
* ...
* };
*/
#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
# define BITFIELD(type) type
#else
# define BITFIELD(type) unsigned int
#endif
