| Message ID | 20241213210629.2525655-1-richard.henderson@linaro.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | include/hw/qdev-properties: Shrink struct Property by 8 bytes | expand |
On 12/13/24 15:06, Richard Henderson wrote: > Before, via pahole: Bah. s/by 8 bytes// in subject; moved to the summary at the end. > 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. Also meant to say, there are 1700+ Property structures in qemu-system-aarch64, so this saves about 28k. r~
diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h index 26ebd23068..1d154c1f23 100644 --- a/include/hw/qdev-properties.h +++ b/include/hw/qdev-properties.h @@ -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 {
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. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- include/hw/qdev-properties.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)