motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-01 23:03:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

include/hw/qdev-properties: Shrink struct Property

Browse source 
Before, via pahole:

arm32, a 32-bit host which aligns uint64_t:

struct Property {
        const char  *              name;                 /*     0     4 */
        const PropertyInfo  *      info;                 /*     4     4 */
        ptrdiff_t                  offset;               /*     8     4 */
        uint8_t                    bitnr;                /*    12     1 */
        /* XXX 3 bytes hole, try to pack */
        uint64_t                   bitmask;              /*    16     8 */
        _Bool                      set_default;          /*    24     1 */
        /* XXX 7 bytes hole, try to pack */
        union {
                int64_t            i;                    /*    32     8 */
                uint64_t           u;                    /*    32     8 */
        } defval;                                        /*    32     8 */
        int                        arrayoffset;          /*    40     4 */
        const PropertyInfo  *      arrayinfo;            /*    44     4 */
        int                        arrayfieldsize;       /*    48     4 */
        const char  *              link_type;            /*    52     4 */
        /* size: 56, cachelines: 1, members: 11 */
        /* sum members: 46, holes: 2, sum holes: 10 */
};

arm64, an arbitrary 64-bit host:

struct Property {
        const char  *              name;                 /*     0     8 */
        const PropertyInfo  *      info;                 /*     8     8 */
        ptrdiff_t                  offset;               /*    16     8 */
        uint8_t                    bitnr;                /*    24     1 */
        /* XXX 7 bytes hole, try to pack */
        uint64_t                   bitmask;              /*    32     8 */
        _Bool                      set_default;          /*    40     1 */
        /* XXX 7 bytes hole, try to pack */
        union {
                int64_t            i;                    /*    48     8 */
                uint64_t           u;                    /*    48     8 */
        } defval;                                        /*    48     8 */
        int                        arrayoffset;          /*    56     4 */
        /* XXX 4 bytes hole, try to pack */
        const PropertyInfo  *      arrayinfo;            /*    64     8 */
        int                        arrayfieldsize;       /*    72     4 */
        /* XXX 4 bytes hole, try to pack */
        const char  *              link_type;            /*    80     8 */
        /* size: 88, cachelines: 2, members: 11 */
        /* sum members: 66, holes: 4, sum holes: 22 */
};

Afterward there are no holes in either structure.
For arm32, size 48, padding 2, saved 8 bytes.
For arm64, size 72, padding 6, saved 16 bytes.

Saves 20k from qemu-system-aarch64 on a 64-bit host.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Lei Yang <leiyang@redhat.com>
Link: https://lore.kernel.org/r/20241218134251.4724-22-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Richard Henderson 2024-12-18 07:42:48 -06:00 • committed by Paolo Bonzini
parent 5fcabe628b
commit ef1ac71ff0
1 changed files with 4 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

8
include/hw/qdev-properties.h
View file

@ -16,17 +16,17 @@ struct Property {
const char *name;
const PropertyInfo *info;
ptrdiff_t offset;
uint8_t bitnr;
const char *link_type;
uint64_t bitmask;
bool set_default;
union {
int64_t i;
uint64_t u;
} defval;
int arrayoffset;
const PropertyInfo *arrayinfo;
int arrayoffset;
int arrayfieldsize;
const char *link_type;
uint8_t bitnr;
bool set_default;
};
struct PropertyInfo {