Pack gap bit into size field's LSB #26
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Reduce `ringbuf_element_t` from 8 bytes to 4 bytes by encoding the "gap" flag into the LSB of the size field. Since all payload sizes are padded to 8 bytes, the lower 3 bits of size are always zero, making it safe to reuse bit 0. This shrinks the per-element header.
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devarajabc
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jserv
reviewed
Oct 1, 2025
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| #define RINGBUF_PAD(SIZE) \ | ||
| (((size_t) (SIZE) + 7U) & (~7U)) /* size is padded to a multiple of 8 */ | ||
| #define GAP_MASK 1U | ||
| #define SIZE_MASK (~GAP_MASK) |
jserv
requested changes
Oct 1, 2025
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Reduce
ringbuf_element_tfrom 8 bytes to 4 bytes by encoding thegapflag into the LSB of the size field.Since all payload sizes are padded to 8 bytes, the lower 3 bits of size are always zero, making it safe to reuse bit 0.
This shrinks the per-element header.
Summary by cubic
Packed the gap flag into the size field’s LSB, shrinking ringbuf_element_t from 8 bytes to 4 bytes. This reduces per-element overhead and can improve cache locality.
Refactors
Migration